I'm tempted to try this. I know our tanks can do 2600 between them assuming they suck hugely. which means the two dps only need to do like 2900 dps to down him within the 5 minutes. And 1 healer to keep everyone alive. I wouldn't think this would be hard at all. Here's who my guild would throw at it:
Maintank: Prot Warrior (1300 dps minimum)
Offtank: Blood DK (1900 dps minimum)
Heals: Resto Shaman (Heroism!)
DPS1: Ret Paladin (25 man I can pop 4k, this group is almost full melee buffs)
DPS2:Fury Warrior (25 man he can pop 3.7k this group is almost full melee buffs)
all that we need is 8111k raid dps. I'm tempted to try a 4 man in a month or so with our OT in his defense heavy gear + dps gear and full unholy dps spec. He should break 2500 then. I'd bring in my mage though for the deeps.