No matter what you do, whenever you go inside Icecrown Citadel you are abusing some kind of a bug mainly because of how Molten Works atm, there is always atleast one class that has something thats bugged on him in a positive way(Seal of Corruption, Frost Strike, Glyph of Holy Light, Ignite, Chimera Shot etc.(and the list goes on and on)). So your point is what exactly ? That ppl should even play this game but instead go play Checkers in Dalaran so they don't have to abuse anything ?
So yeah Diffraction might have abused Priests with their Empowered Renew, but instead of abusing 2 bugs at the same time which would be Emp Renew and the fact that Clouds don't reset in the Dream Realm, they chose and actualy succeeded in abusing only 1 of the bugs, so before you jump on them try thinking a little but, bacause lets not forget that VDW is also loosing her Health faster than it should normaly do it.