Is there some sort of diminishing returns system, where repeated use of the same ability receives less success the more they're repeatedly used on the same target?

i.e. I've been able to cast Demrris' Resolve on someone, prep it again and ready it for when they come out of the stun and cast again a few seconds afterwards.

Likewise, Gorteous was able to keep me immobile with 30x use of that Wail Roar by using the same method -- basicaly just wait for it to drop before doing it again repeatedly.

~ Leilond
http://i67.photobucket.com/albums/h307/ss1shadow/Leilond_Progression.jpg

Wernt stuns and similar forms of crowd control (or at least stuns) supposed to have a period of invulnerability after wards where it couldnt immediately happen again to prevent chain stunning/cc? Or em I smoking something?