I can't say that I've had any issues with Hastur's debuff. But then again I am running 6% Affliction on literally every single Hime with a single debuff...
... and come to think of it, I mostly use my Wind team to fight Ult Thunder, who has far below average debuff resistance...

Anyway, Hastur has a pretty nice package overall. You got a nuke, a debuff, and a teamwide buff. That's certainly above average. Just... nothing stellar. Especially if it's against debuff resistant stuff.