@Darcin Noxious Gust will hit all chars above the one that's petrified so if it's on tank no one dies, but if it's on healer everyone but healer will die.
Grunzer you can get demonify skill from occult tree and let your chars other than tank die so they can attack while dead. Sargaris you gotta spam heal whoever he uses channel health on until it heals him to full and breaks his barrier.
I have no trouble beating any of the bio bosses on insane, however I do have a lot of ascensions. For Sargaris you have to heal whoever he casts channel heal on until you heal Sargaris to full which will eliminate his barrier.
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 "Crusaders of the Lost Idols"){kind=icon}