Damn, I missed the boat on free gold. Oh well.

I did this easily with my DKs. I did 1x Blood, 3x Frost all in PvP 371 gear, and pugged a healer. The healer wasn't really needed but whatever. Killed him in 38 seconds.

I also did this with my Paladin + 3x Elemental Shaman + 1x Resto Shaman all in iLevel 348 gear. It was easy, but healing was required as my gear is a tad low.

I also did it with my 5x arcane mages. I queues with my tank + healer, kicked both then invited my 2 other mages.
I blew all my cool downs, including time warp, and killed him in 14 seconds

Coren only has 1.3 million health or so.