As I see it for that Uber you need several things:
- poison length reduced - you get it from charms and MO your rings and amulet
- max poison resist - ideally around 85 - 90
- a lot of def and physical resist - so min around 200 k def and 25 resist if you know what you are doing and have fast reflexes
- you need summons when you go to the narrow pathways that lead to the boss, in order to distract the mobs
-finally you need the damage to kill the boss fast enough
Final tip there is a sweet spot where you can teleport just before the ramp where the boss is. It's inside a tower. Nothing will be able to reach you there and you can replenish your belt with potions and get ready for the final run.