Update: I have purchased Atlantis and shifted a few skills around to free up the necessary 16 points to invest in the tree. To be honest I was very surprised at the difference this made, my avenger has little to no trouble in Legendary now. I'm working my way through act 5 now which will be my first go at act 5 legendary difficulty.
My next goal is to pick up a Stinger and then research what other MI's are suitable for my toon that have been added in the new DLCs.
If anyone want's to know, my skill tree looks like this
https://www.kirmiziperfect.com/titancalc-anniversary-edition/TitanCalcb285b285b285.html?mastery=Avenger&master1=7&master2=1&sa=24&m1=40-0-0-6-12-12-5-0-1-0-6-8-12-1-8-10-6-0-6-12-6-4-0-0&m2=40-12-0-8-12-0-0-0-0-0-10-0-0-0-0-0-0-0-12-0-0-0-0-0My equipment is:
Head: Hallowed Alala of Legends + Crystal of Erebus
Torso: Exalted Ismenes Cuirass of the Glade + Boar Hide
Feet: Dazzeling Batricous Greaves of the Pegasus + Hermes Sandal
Arms: Hale Palioxis of the glade + Jade Emperors Serenity
Necklace: Myrmadon's Pendant
Rings: Apollo's Will and Archemede's Cogwheel
Weapon: Relentless Bramblewood Bow of the Betrayer + Incarnation of Anubis' Wrath
Artifact: Sigil of Bast