Apollo = Seer
Ares = Warrior
Artemis = Hunter
Athena = Defender
Dionysus = Bacchant (the common name of a priest of follower of Dionysus)
Hecate = Sorcerer (since Hecate use many types of magical skills, I chose this instead of Theurgist or Necromancer)
Hephaestus = Artificer (the follower of Hephaistos is much more than a simple blacksmith)
Hermes = Rogue
Zeus = Priest (I moved Stormcaller to Poseidon + Zeus)
Seer + Warrior = Harbinger
Seer + Hunter = Haruspex (in Ancient Rome - a priest, who practices divination by looking the entrails of animals)
Seer + Defender = Templar
Seer + Bacchant = Ritualist
Seer + Sorcerer = Hierophant (a priest who interprets the sacred mysteries. He was the leader of Eleusinian Mysteries, connected to the underwold, Persephone and Hecate)
Seer + Artificer = Pyromancer (literally "fire-diviner". I put it here, as both classes are fire-based)
Seer + Rogue = Minstrel (the original greek words are "aoidos" or "rhapsode" used for a wandering poem singer in Classical Greece)
Seer + Priest = Oracle (a seer-priest who connects with a deity to receive advice or prophetic visions)
Warrior + Hunter = Slayer
Warrior + Defender = Warlord (both Athena and Ares are related to war, and combined they should make the perfect commander)
Warrior + Bacchant = Zealot (frenzied and ecstatic fighter, no better name I think)
Warrior + Sorcerer = Warlock (I imagine this one similar to Geralt from the Witcher series)
Warrior + Artificer = Battlesmith (Both skilled warrior and craftsman)
Warrior + Rogue = Wardancer (a swift and agile fighter, mostly dual wield. The word "Assassin" is arabic and doesn't fit much in Ancient Greece imo)
Warrior + Priest = Warpriest (self-explanatory)
Hunter + Defender = Sentinel (I used Warden elsewhere)
Hunter + Bacchant = Wanderer ("Ranger" always made me think of Lord of the Rings)
Hunter + Sorcerer = Demonhunter (A hunter of evil spirits, I never liked "Bone Charmer" tbh)
Hunter + Artificer = Trapsmith (a hunter-mechanist)
Hunter + Rogue = Brigand
Hunter + Priest = Augur (a roman or greek priest, who practices ornithomancy - seeking omens in the flight of birds; "bird-diviner")
Defender + Bacchant = Warden (a forest protector, i think Warden sounds more forest-based than Guardian)
Defender + Sorcerer = Soulkeeper
Defender + Artificer = Armourer (both masteries will buff armor, another name for a tanker
)
Defender + Rogue = Vindicator (means defender of justice or liberator)
Defender + Priest = Palatine (an older word for paladin, from the time of the Roman Empire)
Bacchant + Sorcerer = Shaman (nature + spirits + using drugs and alcohol
- it fits imo)
Bacchant + Artificer = Conjurer (word is closer to crafting than Summoner)
Bacchant + Rogue = Enchanter (more relater with charming than Illusionist)
Bacchant + Priest = Thaumaturgist (means "wonder-worker")
Sorcerer + Artificer = Alchemist (I think if fits well both masteries)
Sorcerer + Rogue = Dreamwalker (both Hermes and Hecate can travel between the physical and the spirit world)
Sorcerer + Priest = Theurgist (means "divine-worker", a sorcerer who connects with greater spirits and deities for power)
Artificer + Rogue = Saboteur (trapper/bomber, a more fantasy Odysseus with his Trojan Horse)
Artificer + Priest = Thundersmith (The Elder Cyclopes are all Thundersmiths, forging Zeus' thunderbolts)
Rogue + Priest = Apostle (I imagine it something like wandering sage and preacher)
----
Changes:
Seer + Rogue = Minstrel (changed from Chanter, the latter sings only psalms)
Hunter + Sorcerer = Demonhunter (changed from Shaman)
Hunter + Artificer = Trapsmith (changed from Flameslinger)
Defender + Sorcerer = Soulkeeper (changed from Soulbinder)
Defender + Artificer = Armourer (changed from Fortifier)
Bacchant + Sorcerer = Shaman (changed from Sacrificer)
Bacchant + Rogue = Enchanter (changed from Trickster)
Sorcerer + Rogue = Dreamwalker (changed from Planewalker)
Also changes in Poseidon classes (I put them last because I'm not sure if this mastery will be included):
Poseidon = Seаwalker
Seawalker + Warrior = Corsair
Seawalker + Hunter = Krakenhunter
Seawalker + Artificer = Earth-shaker (an epithet of Poseidon as bringer of earthquakes)
Seawalker + Defender = Sea Warden
Seawalker + Rogue = Argonaut (alt is Swashbuckler)
Seawalker + Bacchant = Wavespeaker (like a sea druid)
Seawalker + Sorcerer = Sea Sorcerer
Seawalker + Priest = Stormcaller
Seawalker + Seer = Forecaster (foretells sea storms and the future as general)