Currently the epic drop rate in raids has been buffed significantly. We have a group of 7 people clearing the trash up to halfus, running out, and reforming raid. The trash respawns instantly this way.
We have gained at least 1 epic per run this way for the past 4 runs, plus the huge amount of gold from that trash anyway.
It is not exactly an exploit, because blizzard caused it, but I can see no way it will not be changed soon because our group got 8 epics in 2 hours already.