This is taken from another well known forum which i will not mention.
But it would explain why certain guilds had a lot of druids on the kill.
This information is floating around already, however, I've not seen it here.
During the Nefarian encounter, phase 1 and all of phase 3, five raid members(25 man) are randomly MC'd and must walk towards a portal. If you reach the portal, you die. You get two abilities, one that stacks a buff on you increasing the damage or healing of your next spell, the other breaks the MC.
Stolen Power
As you can see, it stacks to 150. Normally, this would only make one attack do a massive amount of damage, however, with the use of a feral druid's Rip, the damage of each tick is increased by the damage amount, not the attack as a whole.
This leads to 500k damage rip-ticks depending on how much of the buff you've stacked.
Stack a few feral druids, and you're doing 4-million damage per druid who gets to use this small bug.
Unknown if there are any other DoTs it works with, but so far, none aside from Rip.
I do not claim credit for finding this, but merely think it deserves to be here for those who don't read elsewhere.