Yes, it can stagger bosses, at least enough to hit CS out of the grab. Didn’t do it always, as in the beginning it hardly staggered anything.
As for its use, I’ll blatantly quote (well, link) my own older post: Battle Wizard Fire Walk - Usage - #24 by Yzneftamz
In short, I’ve felt that however I use the skill, I don’t use it well. Use it for one aspect, and I feel I’m not utilizing the others, and it doesn’t feel that strong on either one.