It seems to be 40% for all difficulties, they transitioned at 40% for LFR for my group about an hour ago
That makes no sense if they don't nerf for example adds HP to compensate for increased difficulty in earlier phases...
Love the change, this way you dont have to hold damage to not phase the boss to early!
Yep, this happened to Liquid on Mythic, someone here had it happen on LFR, and it happened to me on a Normal alt run just now.This seems to be universal.