Quote Originally Posted by Theimperfect View Post
dps only need to be at 50-60% hp throughout the fight until the end. DPS/tank need to be interrupting EVERY cast he makes.
They can stay at 20% HP as long as they don't suck at interrupts.

Party damage before Calamity is limited to Pain and Suffering (which DPS should interrupt immediately) and Wracking Pains, which you could reliably leave people at 20-25k HP to live through.