Vasuki (March 2020)

Overview

Mad Gasser will only proc auto-Barrier Break at the start of the round. If you recast Barrier they have no way to remove it, almost trivializing the whole fight.
- Alternately, you can inherit Null Poison or bring demons immune to ailments like Kinmamon to alleviate pressure off your Barrier caster.
Both Vasuki and Hel have a passive that increases damage done to poisoned enemies, and Vasuki will cast an almighty-AOE when your demons are poisoned. If you used the approach above, you will never run into this scenario, severely reducing the entire team's damage output.
With proper buffs and debuffs up, you can mitigate the damage to a very manageable level.
- Hecatoncheires is a good choice for this fight, as he reduces AOE damage taken from both Hel and Vasuki, and can also double up as your debuffer / secondary Barrier caster.