If that poison stun DR is really kept separate through out MoP then this talent would be very valuable, but I don't see it happening. It's like Mace spec proc back in TBC; it was just too much to handle for any class.
I don't expect this change to go through at all. Random stun on top of stun on demand? yeah blizzard will never hear the end of how OP rogues are.
Don't forget, you can not use Crippling Poison with it.
So, you basically don't have a snare. That's a pretty big trade off!