heroic mode is extremely hard, those pats are impossible to defeat, so you have to play around them.  If you have a good rogue he can stealth threw and lay all the bombs and shortcut you to the first boss.

while escorting thrall the mages have about a 3k aoe, 4k instant blasts, the warden dispells CCs and heals for over 16k, and the melee units hit for an extremely hard amount. 

The second boss has a nasty consecrate but other than that is easy.  The last boss must be the easiest because the mobs he summons go down quick, and other than that its just a tank and spank.

we spent 3 hours in there but eventually got it down, the group was:

BM Hunter
resto druid
prot warrior
combat rogue
shadow priest

MC helps alot, if you have a shadow priest have him MC the mages for the mobs and aoe the shit out of everyone, while the other dps is beating on the warden.

I hope this helps for heroic, if you get threw it, congrats.