This dungeon including Thag can be done fairly easily with warparty and corrupted authority too. In AoS and AoW I run 2 geared zerkers wearing all str% gear with str elixirs and momentums (i used tenderizer pre AoW). They typically kill him with only 1 are phase and 1 skeleton phase though sometimes the skeletons are still up when he dies.
The only thing of note for fighting him this way is you need to be on your toes during the ages because they hit hard. They won’t 1 shot you but they will 2 shot you if you get hit a 2nd time before the thralls heal you.

I typically run:
Str: 0
Agi: 0
Vit: 15 (15 corrupted)
Auth: 20 (19 corrupted with warparty)
Grit: 10
Exp: 15

For gear I usually wear Ranger armor for the +agi dmg and stamina on every piece.

For thrall gear I use Executioner’s hood, dragonbone ribs, godbreaker gauntlets, and hyperborean pants and boots.

This isn’t even a pure damage build its an all rounder so I don’t have to swap builds to farm or do dungeons and bosses.