My Suggestions:

Megalesios:
You may need to use his leash range, run away until you get to the point where he returns to his starting position, near the stairs. Fight him there and try to get him and the demons to uncouple by moving around the leash spot, then kill them quickly.  Against Megalesios himself, you might try to get more vitality res from things like Essence of Aegis of Athena shield or Demon's Blood jewelry.

Juggernaut:
If played as a melee character, this class is characterized by its lack of OA bonuses, like many other Defense characters. In Normal you may find enough OA items to get by but in the later difficulties this weakness has to be dealt with somehow. In general, if dealing physical or piercing damage in melee and you aren't critting, you should get more OA.
Shield Smash helps deal with this by way of lowering the opponent's DA, but from my experience this should only be relied upon for bosses unless you are a Monk with Achilles' Shield. Flame Surge also has an effect that lowers enemy DA, but it requires a high level for the debuff to be good enough and it requires its later passives to buff its other attributes, even when not using it to deal damage

Leveling strategy: In general, relying on skills that deal fixed amounts of damage to kill things is much more reliable when starting out. A character with godly gear can outpace spells but early on you can do huge damage reliably just by pumping a specific spell. For Juggernaut I would recommend a Defense dip / Earth pump strategy but I see you already have Colossus Form so we have to think of something different!

Some suggested Defense skills:

Armor Handling: The requirements reduction is useful, but the "Armor Absorption" property is integral to Defense because along with Quick Recovery, it allows you to rely on a high armor to reduce pretty much all of enemy physical damage. Someone can correct me if I am wrong but by default, armor reduces up to 66% of incoming damage, the rest is taken in full. Armor Absorption increases the ratio, in other words, reduces enemy armor penetration. And so, since ultimate AH + QR add to 34%, it means that having a high enough armor can prevent all damage taken. Because you already have a lot of stats from pumping Defense mastery, this might not be needed to be maxed quickly, depends if you think you are dying too fast.

Quick Recovery: Even though this is a cooldown, the uptime ratio is one of the highest around. At ultimate level it is 3/4 so you only need 25% recharge reduction to have it up almost constantly. Look for unique weapons and shields with -recharge, keep them in your second weapon set and swap to that to cast QR with. A typical goal for Defense gearing later on is to have enough recharge to be able to cast QR and Rally at 100% uptime without weapon swapping.
Anyway, what QR actually does is increase armor absorption, increase shield blocking and block recovery. Block recovery in other words is block cooldown, and 2 seconds by default, so blocking by default does little against crowds. QR eventually reduces the cooldown by a huge amount. Be sure to upgrade to better shields as they become available.

Batter: 1 point is fine to begin with, and 1 point in the passive. Shield attacks attack with the weapon too even if the animation doesn't show it. You can put this on your left button so it's used automatically when attacking whenever it's up which is a good idea because Juggernaut doesn't have a dedicated LMB skill.

Shield Smash: Attacks with both weapons as noted, plus the -50% DA property causes enemies to get owned by subsequent melee attacks which is  mainly relevant against bosses.
Disable, Pulverize: As before, but the bonus effects are different and Pulverize hits 3 enemies.

Earth:
Volcanic Orb: good split fire/physical damage at a reasonable cooldown.
Ring of Fire can be pretty powerful but the energy drain can be an annoyance, and you can't rely on getting big energy regen items in the early game.
Heat Shield: 1 point is plenty. 15% physical res at 100% uptime is great for anyone.
Stone Skin, Stone Form, Eruption, Volativity: when they become available.
Note: any more than 1 point in Stone Form is useless, because the potion cooldown is shorter than the duration of SF with 1 point in Molten Rock.

OK looking at your skills I'll assume that with 55 total points at this stage, 32 in Defense and 1 in Earth:
33 on masteries; 22 unspent. The skills added up to 19 so maybe Earth is at 4. Going for a defense dip/earth spell strategy at this point is unworkable, so I think spending aggressively for a fighter spec might be the best here:
3 Armor Handling
4 Shield Smash
4 Pulverize
1 Disable
1 Batter
1 Rend Armor
1 Shield Charge
1 Disruption
1 Quick Recovery
1 Colossus Form
1 Heat Shield (up at ALL times)

Megalesios hits harder with spells than melee so no maxed AH yet. EE doesn't really do anything if you don't have fire or burn damage to multiply, so no points in earth yet. Remember that Shield Charge can be used in melee, with +1 extra target from Disruption hits 2 enemies with weapon and shield for a total of 4 hits, you can use that too against the demons. Shop for a better weapon if you can afford one. Favor quicker ones (sword) over slower (club/spear) at this point, very low attack speeds (under 100% or so) are really slow and proc bonus damage like the shield procs less efficiently. Cast Colossus Form with -recharge items if you can, since the cooldown is so long.

The important thing here is to get past Megalesios, Egypt is easy and you get 4 free skill points from quests there, just be sure to have a good amount of poison resist (Pristine Plumage charms) for the first boss, in the library.

Following points I would spend:
-max AH
-max pulverize
-max shield smash
then,
-disable
-1 point in battle awareness and passives (probably don't need more DA yet because of the dex from defense mastery, focus is good but I think QR should be maxed first for blocking)
-volcanic orb or ring of fire, then earth enchantment
-QR gradually, more quickly if you find good -recharge items. Late act 3 and especially act 4 will be big difficulty spikes and QR will be wonderful then
-adrenaline, resilience, defensive reaction (DR is the important one here, but you should have good attacking from maxed shield procs, good weapon, etc. first)
Prioritize based on whether you feel you need more offense or defense. Note that scaling stat doesn't really matter in the early game, you can use any damage type as long as you put enough points into the corresponding skill.

Not going to lie, going so deep into Defense that early on seems like a big challenge, but it can work out if you find good weapons. Look out for "Veteran's" or "of Reckless Power" weapons on merchants, once in Egypt you get better max selling prices from vendors and more space, pick up stuff preferring valuable (dual affix) and efficient (jewelry) items to vendor, habitually look for better weapons on traders and blacksmiths. Don't wait too long to drink potions, running away and drinking allows you to beat anything. Good Luck!!!!

Many Neidan skills were shifted around in the tree, just when we were getting used to the positions..
Undocumented changes that I saw:

Skill tier changes:
Essence of jade (now called Inner Equilibrium) now 4 instead of 10 (old functionality in Potent Elixir; this is essentially a new skill)
Breath Attack (now called Dragon's Flame) in 4 instead of 1
Terracotta Servants in 10 instead of 16
Chi Realignment: now 16 instead of 10
Smoke Cloud: now 1 instead of 4

Skill changes:
Chi Realignment: Energy Leech duration rises with level (maybe it was always like this, I haven't used it...)
Reverberation: also has 10% chance to petrify for the same duration as other debuffs
Blessing of Jin Chan: tooltip says that the amount of treasure grows with each level. Chance stays at 3.0%
Many skills have their descriptions rewritten to be more clear, for example, Shen Pao now mentions that it transmits weapon effects (it was always like this, but not written on description). Consequences now mentioned to proc on "attacks", and indeed even damage reflection from AoT+MA seems to proc it still, so maybe this is the intended way after all. Haven't been around enemies triggering the bug yet to see if it's fixed

Second legendary orb dropped this 
https://i.imgur.com/qhVYPRV.jpg

Welcome to the forum.   

Nice to see a summary of the new Neidan mastery.

Thanks 
Here is the last part.

Character Ideas...

Channeler (Neidan/Storm)
One of the most obvious. You could be a caster using Shen Pao (or Breath Attack) and Squall, boosting the former's damage with the aforementioned Storm Nimbus and elemental damage items. You could be an elemental damage fighter character, using something like Mjölnir or the newly fixed Elemental Reaver, boosting your elemental damages with Storm, and boosting defences with Neidan and hitting hard and wide with Huangdi's Favor. Squall will of course be a very helpful centerpiece, as with all Storm characters.

Wu (Neidan/Earth)
Poor predictable Earth has some bones thrown its way. Forged by Fire has some delicious synergy, Huangdi's Wrath can effectively spread Burn Damage from Laevateinn, and you need not look any further for the most potion-addicted character-- simultaneous use of a maxed Ring of Flame and Aura of Tranquility results in a horrific amount of energy needed every second, which in theory can be countered by nonstop energy potion quaffing.... Shen Pao might also be used for AoE burning, though the damage will be lesser as it can't get the burn damage directly from weapons.

Contemplator (Neidan/Dream)
I've not given this a lot of thought, to be honest. Missile avoidance can easily be boosted to a very high level, and Master Mind will help the terracottas a bit, as will Trance of Empathy.

Daoist (Neidan/Warfare)
Unsure whether the name is a pun or not-- Daoist can refer to taoism (Daoism) or possibly to the Chinese sword, dao. Anyway, both physical resistance and avoidances can easily be boosted to very high levels. Again, Onslaught can be kept up with lesser enemies, and Huangdi's Favor reserved for big crowds. Many pets with ancestral horn, terracottas, dual Keys of Elysium, boosted by flag and consequences. Physical caster/melee hybrid using Shen Pao and Slam. Etc....

Spiritualist (Neidan/Spirit)
Let's pretend that the best strategy isn't to run into enemies and kill them in one hit with Soul Drain/Necrosis... The Vitality damage from Weakest Chakra should prove interesting with the Spirit buffs, Horny and mind controlled enemies-- although playing on xmax will become a necessity to keep up with the enemy levels. Another flavor of melee character that debuffs enemies with Deathchill Aura, then carves them up with Huangdi's Favor: both armor and physical resistance will be swept aside.

Monk (Neidan/Defense)
No-nonsense fighter character that gets quick Huangdi's Favor hits with the shield procs, going physical or possibly some magical damage spec. In any case, Armor Handling will help with the strength armor while the intelligence will help with the mage armor: I was thinking of using my last Paladin gear with this, something like Starkad's Wife, Achilles Shield, Odysseus Armor, Archmage's Clasp, Stheno's Wisdom, Hervor's Fine Steel, Talisman of the Jade Emps.... Damage reflection should work. Some kind of -recharge pet character spamming Perfect Block. Should also be the undisputed class for regeneration spec. Many options here.

Hermit (Neidan/Nature)
Obvious pet character, as before. Super tanky with Heart of Oak, Overgrowth, etc.. Ruins enemy resistances with Plague + Consequences. Physical fighter character should work too, with the physical damage buff from the wolves and Overgrowth halving DA.

Esoterist (Neidan/Runes)
The obvious "battlemage" archetype should work fine here. Shen Pao should also benefit from Elemental Charge. Breath Attack should also work as an intermittent Rune Weapon-boosted damage spell. Probably the widest range of resistances buffed. Energy Armor clashes badly: needs -%Energy Cost, when Neidans want energy regen to counteract AoT. Not that I usually even bother to use EA...

Pilgrim (Neidan/Hunting)
Spear Pilgrim using Huangdi's Favor as LMB should be a winning combination. With a ranged weapon the decision becomes more tricky. There's no real reason to use both Marksmanship and HF considering they are both mainly AOE skills. HF is probably the more attractive choice for thrown weapons since the reduced range does not affect the explosion's potential, like it does for the "piercing" property. As noted earlier, Shatter should prove deadly with Hunting. Some kind of magical Pilgrim might also work although you will need to get elemental or vitality damages from somewhere; enemy resistances on the other hand are ruined by Study Prey + Consequences. Some piercing or bleeding staff might also work, getting the damage boosts from Hunting and the exploding autoattack and defenses from Neidan, although overcoming the high intelligence requirement remains a large obstacle.

Disruptor (Neidan/Rogue)
As you can see, the Gorgon's Edge poisoner works fine. Other ideas: pet disruptor with traps and terracottas. -Recharge shen pao rogue. In any case, prospects are looking grim for Calculated Strike, although it might be good for single-target, non-Humankind bosses, since it doesn't need a lot of points to max it.

And early thoughts on Neidan overall...
So what kind of mastery is Neidan after all? Caster? Fighter? Dominant? Supportive? Good? Bad? The in-game description is rather fluffy like that of Dream and does not describe its typical capabilities. At this point I would consider it a hybrid, the most hybrid-like mastery so far. There are strong defensive buffs, with some loaded dependency on mana regen/Potent Elixir. There are pets. Casting capability dealing mostly elemental damage. Spell conveying weapon effects. Strong, AOE-focused LMB. The 4 usual suspects that prove useful for any other mastery are probably Aura of Tranquility, Huangdi's Wrath, Potent Elixir and Consequences: AoT provides excellent defenses, HF is strong as discussed, and PE not only fuels AoT, but can substitute for energy regeneration or -cost for hungry spammable kill skills like Throwing Knife and Ice Shard. And Consequences of course acts as a force multiplier for whatever damage or pets you have.

As for what Neidan DOESN'T have: offensive or defensive ability, any kind of speed buffs (for now), special melee abilities, many party buffs (though Consequences is a potent debuff). Many of the downsides can be compensated by specialty gear, which in addition to the aspects and strengths of Neidan that are not immediately obvious, makes me think that the mastery is something geared towards players more experienced with the game, to go with the Legendary-exclusive act 6.

Fluff-wise, I was expecting some Kung Fu mastery for a China expansion, but this is even cooler. It is even more specific and themed than Runes, though, which you may or may not like. Who said like "WTF is Neidan??" when they first heard about it? I know I did. But therein lies the idea: calling it the "Alchemy" mastery would exclude the internal, mental abilities that are also essential to Neidan's identity. Of course, the less narrow identity is what you might precisely dislike: Neidan is something that could work as a complete class in another game, whereas "Defense" or "Storm" are considerably more generic, fit for the dual-class design of TQ where you take two of something generic and make something unique. Here you could mention the supposed original design where the masteries represented specific gods but which was axed by THQ, but I digress...

Act 6
The first thing you'll notice is that the voice acting is a marked improvement from the "quality" of Ragnarök and Atlantis, although some of the voices are oddly familiar-- did they suddenly start caring? The second thing is the pair of chests containing welfare gear-- a semi-set of decent armor with no requirements and a -20% exp penalty each, and some old, Epic-difficulty uniques, plus a Symbol of the Polymath with no completion bonus. Is that garbage really enough for what is advertised as the ultimate, most hardcore challenge for the most elite of Legendary characters only? Well, possibly, since the difficulty seemed rather mild, at least coming from 3x xmax using what isn't exactly trailblazer gear. In fact, the most difficulties, or even the only, came from the Consequences bug. Apart from that, I didn't seem to encounter any really nasty enemies like the Black Elves in Ragnarök or the Atlantis archers that made Machae seem like kids with slingshots. The trickiest monsters were actually the good old draconian mages making a reappearance... you know, the sort that shotgun-blast thunderballs and do that orange damage shield. I will probably need to play it more with xmax and other characters to really assess the difficulty of the monsters. The two last bosses stand out as the most interesting of the lot.
For the record, I took Ylva with me, and as expected without pet bonuses, she was a modest help. The final battle was her last; she will have quite a tale to tell in Valhöll.

Overworld & underworld
As for the areas and the general feel. It's big. Like, REALLY big! Act 6 makes Act 5 seem rather modest and Atlantis downright minuscule. If you fully clear every area, it will take you days of playing to solve everything, and that's just with one character. Making Act 6 legendary only was really a good call, I think, because I can't imagine it being anything else than an incredible slogging inbetweener on Normal and Epic that would not stay relevant long for many people.
Every zone feels like it has taken a hint from areas like Scandia, being a huge net of nonlinear maps with secret areas and chests placed at every opportunity. The dungeons are a massive step up from the previous small generic caves and tombs that take a few minutes to visit. You go to some cave, it has a unique name, and you pass through a token underworld area into a huge, handcrafted (even with the cannibalization of assets from previous acts) dungeon area with tons of length, enemies and chests. Looks like some main quest area. But it's not! Not even a sidequest. It's just some random dungeon on the way. This keeps happening all through act 6. This is interesting because earlier I actually was hoping for some larger, bigger dungeons in TQ because repeatedly running some boss or short areas can get boring quickly-- a somewhat bigger singular area that takes longer to play through, like the Pit or something in Diablo 2. And then they did just that. The side dungeons of EE make the old ones look like a joke.

And then the overworld itself-- on the portal map it's called "The East." Doesn't Orient mean just that? Then again, for those who feel that act 3 felt rushed or irrelevant in respect to the local mythology, I don't think they need to worry. You could say about act 6: "I am Orient... or rather, Orient as it should have been." The careful presentation, music, atmosphere, variety and improved voice acting all combine to make for a very pleasant experience. One thing that might surprise you greatly is that, at one point, the game goes like "By the way, you need to go to Egypt now." And so you go. The Egypt portion of act 6 is only 3 portal areas long, but honestly, long enough to be its own act. If you liked Egypt, Lower Egypt should not disappoint. Trekking through the rocky wastes and robbing ancient tombs while bashing mummies & skeletons are activities that will again become VERY familiar in this section. For better or worse, it's Egypt times Egypt. Some old NPCs are seen again, and at the risk of spoilers, there was no attempt to imitate the old voice actor of Imhotep; the performance of the familiar NPCs in Ragnarök was downright heroic in comparison.

There is one very confusing part for me. At one point you are told to go meet the Pharaoh in Thebes. Great! I will just portal to Thebes... but it's the same old hamlet as before. No change. Turns out there is a door you must go through in the new Egypt areas, and it continues... and oh no. They're doing it. They're really doing it. Another huge stretch of overworld and... Thebes. Again! And it's huge. Like the Chinese city you visit earlier, Pingyang, it is really huge, with a modest amount of NPCs to talk to. So what was that old Thebes? Maybe it's the section on the Nile. But then you explore more of the new-Thebes and... river bank. WTF! Did they just really forgot that Thebes was already depicted in the game? What!
Well, one possibility is that the new Thebes is actually on the other side of the river (also an unexpected "The Mummy" reference regarding this that floored me ) even though in-game they are both northeast of it... see, the in-game act 2 Egypt is actually flipped upside down, seeing as how you progress northwest but keep going south in the portal map, likely to deal with the camera system of the game where you see less what is in south of you compared to north. So the old hamlet Thebes is on one side, and the big super Thebes is on the other? I don't know.

Notable there is a new set of "silly" letters which were missing from Ragnarök and Atlantis, although they don't drop from monsters randomly, but are placed on fixed locations. There are some more serious in-universe letters among them, and also books on pedestals that act as gossip NPCs, relating some local mythological story when read. These basically take the place of storyteller NPCs which were, as far as I remember, conspicuously absent from towns.

Sidequests
There are plenty of sidequests, although in comparison to the area to explore they can seem few. Without prior knowledge, you have no choice to but to explore everywhere to find the quest objectives and some of them (Darkstone of Anubis) are anything but obvious. Their rewards are worthwhile. The experience rewards are large and some seem to give specific legendary items as rewards-- will have to see whether they remain worthwhile when done repeatedly. The special rewards are as follows: 2 skill points, 10 to strength, dexterity and intelligence, +10% vitality resistance. Power creep, but you have to remember that these can be gained once only, since act 6 exists only in legendary. The vitality resistance is particularly interesting. A late sidequest gives access to a vendor that sells some EE MI's. The most noteworthy of these is the Strength helm that gives about 29% PR and some other stuff. He is gone from my game now, though, and it seems that this is a bug fixed in the beta patch.

Items & gameplay
The burning question is: do the new items drop? And the answer is NO. Or at least partially. New uniques still do not drop, which is kind of amazing when act 6 is legendary only. What were the testers doing? So don't get too excited at purples dropping... they will be some vanilla or IT stuff.... although I did come across a strange exception: a Lower Egypt enemy wielding Laevateinn (https://i.imgur.com/e1vfTuZ.jpg).
So apart from the quest rewards, legendaries are a bust... now MIs do drop. BUT... some of them never get bonus affixes. Some of them rarely get bonus affixes. Some of them drop almost constantly, and their fixed bonuses are crap. They are really a mixed bag, but they do represent some interesting new items, especially when combined with...
New affixes. Some examples: "of Aten" ~32 Fire res, ~300 Burn Damage over 6 seconds, +20% fire damage, can appear on amulets and body armor at least. "of Set", ~188 bleeding, electrical burn and poison damage over 3 sec, ~15% slowed for 3 seconds, ~+150 OA, can appear on bows at least.
There are new divine artifacts and their recipes do drop. They seem like they have some potential, although reputedly the completion bonuses are crap.
New and old relics and charms do drop as expected. There are only 2 relics that drop in Lower Egypt so you will quickly clutter your bags and stash with those, even when not playing on xmax. Some of them have interesting properties, like poison damage on jewelry. Pet rogue/knife poisoner hybrid with allfather rings + poison relic?
New potions: they drop infrequently but do not seem to be available on any vendor, this seems like a bug. Otherwise it seems like an interesting mechanic to patch holes in your particular build, but in a somewhat temporary & unreliable manner that also costs gold to keep up. They all have a 30 second duration and a 90 second recharge, which they all share. Examples: +70% poison, bleed and life leech resistance. +40% to melee and ranged avoidance. +70% to secondary resists. Also, scrolls infrequently drop from chests. This is a nice addition that reminds you that scrolls exist but which isn't common enough to make buying them seem a waste. Naturally there are also some new scrolls.

Then the important part. Where does this all fit in? We can just list what is added, what are the new items like, etc.. but it is important to note how it all is integrated into the game. The new act is very long, as noted. Quite a bit of playing is required to get the all "character" rewards, which extends the game further. However, being Legendary only, it is not unwelcome as the good stuff can drop, and especially the new good stuff (in theory). So in act 6 we can find the new relics, some new and some old charms, new MIs, new affixes, and at a guess, some act 1-4 and act 6 uniques. Does this supersede all the previous areas? Is act 6 the god area to run? The base item drop design of TQ was designed to balance local and global drops, and to some extend it still works. In AE we can find act-themed uniques spilling to others, same with relics, but MIs especially are still very local. Act 5 still drops its own uniques and charms. (Not withstanding that strange laevateinn... ) Atlantis will too, hopefully. The old acts 1-4 are the most in jeopardy here, possibly by design, because after all, the new expansions don't seem very attractive if the new items all suck.  Then again, by now they are mostly considerably easier than the new acts for very accomplished characters. For experienced players that have most of the good items from the older expansions, it is natural to gravitate to the newest act because it has the most new items. For new players the decision will not be so clear. It remains to be seen what the practical implications of act 6 are for running and character goals.

Apparently there is some beta patch which casually fixes the Atlantis & EE legendary drops among the first few lines of the patch notes. Hopefully they won't take until the next expansion to release a proper patch.
So. Buy or wait? The two big new features of EE, Neidan and act 6 are otherwise fun & well done but both have crippling bugs (Consequences bug, legendary item drop rates) so no matter what you do with the new features, your play experience will be hampered. If you absolutely have to play some new TQ right now, you can, but be warned of the usual alpha-quality launch experience we've come to expect from THQ Nordic. If you can wait, if you have something else to do in the meanwhile, that could be a good idea, but again, with THQN the patch could come in 2 days or 2 years.

I'll describe my character I went through the game with.
I also have some remarks regarding Neidan in general, but that is another 23k characters 



Character concept
Some of the Ragnarök DOT weapons have long interested me yet I hadn't been able to come up with something that really brought out their potential in the best way. In particular, the problem was conveying the dot to as many enemies as possible, as often as possible. Even when not playing in xmax, individually attacking every enemy gets pretty annoying because if you are relying on dots, you should switch targets every strike rather than attacking the same enemy continuously. Some things I tried with Gorgon's Touch and Laevateinn in particular:
Dream - Psionic Touch, Phantom Strike: PT was probably the previous best. With Atlantis' Psionic Beam, every second hit can be a piercing one, carrying also the increased total damage from base PT. It works alright, but throwing weapons travel a shorter distance and therefore their total 'railgun' potential is lessened. Phantom Strike only works with melee weapons, so this was really a Laevateinn thing, and then you will also need a good amount of -recharge and some OA.
Rune - Thunder Strike: Similar story as with PS although this works with all weapons.
Warfare - War Wind: Melee only. Also a cooldown, and as a warfare skill comes with its baggage: basically mandatory Onslaught use and the dual wield question, recharge for banner and ghosts...?
Defense - Batter: Kind of a cheeky one... but melee only again. Much shorter recharge. OA became a problem.
And so on...

Neidan really solved this question in a very practical way: upgraded Huangdi's Favor, the LMB skill, explodes on every second hit in a similar manner to Runeword: Explode. Not only that but it receives a total damage boost on such hits plus a 50% chance for some lightning damage and a short petrify. You can see where this is going: the one-two punch where you quickly attack twice and light up every enemy in a group with a DOT, then move on to the next biggest bunch. Another very convincing and interesting tidbit I noticed on my initial Neidan/Defense Monk: Shen Pao (the potion bomb skill) conveys weapon effects just like Throwing Knife and Blade Barrier. So, another way of spreading the Envenomed Weapon debuffs and also inflict some lighter dots. So I left the Monk hanging and made a Disruptor-to-be. I anticipated no problem with defenses, as Aura of Tranquility is very powerful to begin with and combines nicely with some additional physical resist or avoidance items. As for the energy consumption-- would cross that bridge once I would get there. Let us not even mention the mockery Mandrake and Flash Powder make of melee attackers.

I chose to play on 3x xmax since I already played with Neidan up to normal act 4 so I would already have an idea how it would fare in vanilla. For the new EE areas I would turn it off.

Normal
Chose Neidan first. 1 point into Huangdi's Favor because I will be autoattacking a lot for a while-- all the rest into Neidan mastery. All points there until Shen Pao. Can put a couple of points there, then it's time to choose Rogue Mastery. From then on, EW received the lion's share of the points with the reasoning that this early Shen Pao would kill most of the weaker monsters with only 1 hit anyway, the poison would then be applied to the survivors, and it would also be on my weapon attacks which I would still be using a lot because of the 5 second recharge on SP. It worked fine, similar results to earlygame Distortion Wave pumping where large mobs would get wasted effortlessly. No need to pull the 3x3 gorgons separately, aoe was strong enough to kill them through the heals. Killed some act 5 harpies with SP
Some interesting drops:
Hood of the Magi
Small Torch
Shroud of Eternal Night recipe and +8% attack speed bonus. Nice!
Skeletal Darts with +27% phys damage and +17 damage. Maxed Blade Honing for these and used these for quite a while.
Outlaw's Sash, Shroud of the Night, Brigand's Axe. +3 to rogue was pretty excellent for normal, but you can guess that I was quite reluctant to give these up.
Turquoise Bow. Nice weapon for killing some dangerous enemies like Barmanu or the Typhons with poison from far away.
Nubian Deflector + Ardent Greaves.
Armor of the Tireless Soldier + its 'set' gloves and boots. Scironian Helm. Rings of the Rhine... not bad drops at all.
After much shopping and more killing, my very first Hallowed helm dropped as late as Land's End Fortress. Doh!

Normal went pretty much as expected. Did not go into Atlantis. Shen Pao did the killing, I did not have any good dot weapons yet apart from the bows, but I chose to continue using SP.
Poison resist from oracle!!

Epic
The big baby finally entered Epic difficulty at level 50 and here the twinking started. To be honest Epic is still the annoying inbetweener for me so I did not really feel like slogging through it because I was anxious to get to Legendary. So the Epic express was pretty unremarkable, the NPCs of that world will just have to deal with my ignoring of most of their sidequests.
Another poison resist from oracle!!!!

Legendary
The showtime at Legendary Helos where you realize your dream gear setup totally fails due to bad resists, unrealistic stat requirements or both. Not really this time though. I was planning to use something like Berserker's Mantle + Zeno's Third Paradox + Lyre of Apollo for avoidance (+ AoT) but for one reason or another that didn't feel good, probably needed more resists. I mixed and matched stuff, easier with the bigger shared stash, and did come up with something workable. Initially the second ring was an Archimedes' Cogwheel with -8% requirements but later I could switch it for a Grace of the Alfar. So apart from that, these items were used for acts 1-6 legendary (+ on uniques signifies Durin and Dvalin's improvement):

Gear

Head

Hallowed Stheno's Wisdom + Legendary Crystal of Erebus (+2 skills)
The basic trouble shooter. The problem solver. The skill tiara. My one and only +2 skills legendary erebus was in this, so my choices for headgear were limited: I always want to have at least +4 to all skills, and seeing as how Neidan has no non-EE items boosting skills, this would be difficult. +4 to all skills would have to be gotten from somewhere and this was the obvious solution. Not to mention the PR and cast speed that go very well with Neidan, and of course the big glob of vitality resistance. The problems start and end with the intelligence requirement, fortunately, Neidan comes with some int in the mastery and extra points are not totally wasted since you are going to do some magic damage with Neidan no matter what you do. Base int sits at 118 as of writing.

Ring 1

Persephone's Ring +
Very fortunate big poison resist on the imbue, and a handy strength bonus too. All of the bonuses here are helpful except maybe the cold damage, but it's really the resists why I wear this when I do.

Ring 2

Grace of the Alfar +
Once I got the intelligence problem sorted out, ring 2 was basically a free slot. I chose this because of the avoidance and big dex boost. From the imbue, the DA is helpful, but the LR is not because I already had it maxed out.

Weapon 1

Gorgon's Edge +
What to say. If you want to do poison damage with a weapon, you will probably look no further. Very fortuitous imbue here. +1 to rogue and ~19% requirements are nice if somewhat common separately, but together they are godly here.
Edit: +1 rogue is base! Weightless Rogue's probably can't spawn anyway. Armor reduction is the imbue. Speed would be better!

Weapon 2

Priam's Gate +
Resist shield. Imbue is nice.

Body

Alexander's Cuirass +
Good old Alex Cuirass sees some good use here. The skills are kind of overkill but certainly helpful. The avoidance is very welcome and who can forget the rare bleed duration reduction, which, combined with a high bleed resist, makes a joke of enemy bleeds. Otherwise it substitutes for a higher bleed resistance.

Hands

Gauntlets of the Necrolord +
Big resists. +1 to sklls. Some attack speed. Some life steal. Even some dodge... if you have the the strength and are not in need of some specialist item like Archmage's Clasp, Necro is always a very attractive choice. During Epic I was using Hugin and Munin, it would have been fun to keep using those but I needed the resists and the lifesteal never hurts. I have some other imbue with int but some health regeneration boost is nice to have with the Neidan potion buff.

Neck

Myrmidon's Pendant +
Another of those items with some stuff, and big resists. I really wanted to use Torc of the Ancestors, it's my god item at the time which I'm obsessed to include in every character, but couldn't. Need the resists and that fateful -8% reqs normal imbue. Some projectile avoidance. The War Wind is useless again because melee only, who cares.

Feet

Bandit King's Tracks +
Check it out. I've never seen another unique that got the imbue affixes on its name, have you? Only an Epic-difficulty item, but it's Atlantis so the stats are still impressive and the two green imbue affixes surely don't hurt. Avoidances, some resists, rogue skills. Health and total health. Low armor though. Who knows what kind of crazy Atlantis stuff we would be using if something other than Golden Kris would drop on Legendary?

Artifact

Lyre of Apollo
Rarely for an artifact, all of the bonuses are useful and relevant here. The avoidances obviously, one of those items you use to push through to critical mass of avoidances, but the total strength and intelligence boosts are also genuinely useful for meeting requirements. The Energy Drain and disruption bonuses apply to Shen Pao as well (although I have never noticed disruption doing anyhing to monsters). The energy drain is one of those "nice to have" bonuses even if it is situational, but it probably did help with the huge amounts of undead to fight in the Egypt segment of EE. I had a Pierce and Lightning resist LoA before, which I didn't need, and on the first craft I got this +33 strength one, which isn't amazing but better than nothing.
The spell is kind of funny, but annoying since it is an uncontrollable proc. If it gets reflected you are in for a world of pain...

Switch weapons:
Weapon 1

Dagger of Basbona +
Because of the -reqs on Gorgon's Edge, my switch weapons would also need -reqs to avoid unravelling my gear on weapon switch. This has a helpful -8% requirements and -17% recharge which combines with...

Weapon 2

Rings of the Rhine
Another -15% reqs and... only -15% recharge, this is actually a crappy RotR, I have a better imbued one with -18% recharge, poison resist and regeneration... anyway, the switch weapons are used to cast terracottas and blade barrier with (need to put in an extra point for BB to cast it at max, since my GE has +1 rogue). Also an easy way to get slightly more exp from quests 

Other
Thoth's Glory
For some damage reflect enemies I equip this in the place of Lyre of Apollo to prevent unwanted Songs of Apollo. I can't just unequip the lyre since I depend on its +15% strength and intelligence to equip items, but that can be substituted with Thoth's -20% reqs.

Andvaranaut x2
You should know about this already, but quest reward exp also benefits from +%exp effects. The EE quests give big amounts of exp so I strongly recommend equipping these before turning in to hugely increase the exp reward! Exp from reclaiming gravestone also seems to work like quest exp, so you can actually reclaim more exp than you lost... so just equip a Sacrificial neck, 2x Andvaranaut and other stuff like that, then die repeatedly to legendary helos satyrs on purpose. Only some 700 deaths and you can get from the 60s to 80, ready to equip the sickle of Kronos without the propeller cap of twinking 

Legendary difficulty went basically as expected. The terracottas turn out to be surprisingly delicate, but the Shatter skill makes that a catch-20 situation for them. FINALLY another +2 skills erebus crystal; the tyranny of Stheno is at an end. Undead don't slow me down that much, but what does is the Consequences bug. That is really annoying... to elaborate, from my general Neidan comments:

...The second thing is surely infamous to all Neidans with some experience in the mastery: some enemy skills can cause you to cast this on YOURSELF... and not only that, on some tick interval, it has a chance to refresh based on your skill level. Suddenly having 25 subtracted from your resistances can be deadly if you're not expecting it, and more frustrating still is the semi-random duration, which, if your skill level is high level, could be a few seconds or a few minutes. Countermeasures against this bug include: removing Consequences points when going against particularly troublesome enemies triggering the bug, going to a mystic and taking points away until the debuff goes away, then putting the points back, or casting Spell Breaker on yourself: consequently, Channeler (Neidan/Storm) is a good choice before the bug is fixed because it affects it the least.
 Some skills that can trigger the bug: Ensnare, Study Prey, Black Elf debuff, Deathchill Aura.

EE went swimmingly. The bosses melted quickly from the poison damage, although the massive amounts of undead to fight in the Egypt portion put a damper on things. Lots of extra points on account of the excessive amount of +skills I had. Build basically works as expected. So YES... there is no reason HF can't be used for other DOT weapons as well. The way is clear for Laevateinn and friends to shine!