The most odd comp I see happening in 3's is:
Holy Priest/Boomkin/Death Knight.
Why? Holy priests have good dps and stuns. Main advantage is living a extra 15 seconds since how ridiculous burst is.
The boomkin puts down solar beam (10 second beam, silences if the target is inside of it.), grips healer in it... spam coi for full 10 second silence.. stun afterwords and then strangulate... with a mind freeze on top of boomkin burst, use chastise on mid heal.
It's going to have to be a cleave team at the least.