DK/Rogue/Priest/Warrior/Druid should barely be taking any damage on P3 Black Knight if they save their absorb/damage%- cooldowns for that phase (and they should be). I suspect Mages can reset their debuff stacks with ice block. So either your group comp is really unideal, the tank isn't able to mitigate damage without his CDs in P2 or the DPS is too slow to kill the P3 form before 7+ stacks of the debuff start popping on everyone.
XI Wiki


