It just demands mastery of execution; even if you know the mechanics you just really don't want to mess up ever. Turn 7 is the same way but moreso as you really can't afford to mess up even once where in T6 you could afford maybe 1 or 2 accidental Devours and still manage.
Basically DPS need to get used to mechanics fastest because you don't want them compromising their damage just for survival. You want both.