So the debuff does act like a seperate event per mob. A good wail however will knock a pm out for about a minute. There still needs to be a hard cap.
I walk into a room of 10 mobs, wail and kill 8. On normal even this would drop my dc to a 30 and I wouldn't be able to FoD effectively for 60 seconds - at a dc of 38. Seems a bit harsh though I like the principal. The timer needs to be reduced to 10 seconds or less per tickoff.