I've done this 5x several times, I did it with 5x pally and I did it with pally+4shaman with no problems what so ever.

I'm now trying to do it with my druid-bear , 3xWarlock, priest and I can't do it.
the bear gets silenced at the second swarm and can't taunt the add. the silence last just long enough for it to kill 3 of my alts and usually the healer. I guess I could stone 3 of them but it's really cheesing me that the bear is silence while the pally didn't seem to be.

I've done this with the bear tank and I don't remember being silenced before.