This fight really will push you to the limits of your ability to hold aggro on multiple targets.
Line of sight is your friend here. Duck around a corner, hide in one of the alcoves where falric and marwyn spawn, whichever you prefer, but do something to break line of sight with the ranged so they have to run to you. You can silence the mages and disarm the hunters to make them come to you for a short time as well. Use your stuns and interrupts as necessary.
DPS needs to do their part on this fight as well. Any CC they can use they should use to lock down the hunters. Usually I can get the mages to come to where I want them to by using heroic throw + taunt or charge > shield bash. I'm assuming you're talented into Gag Order, of course. Also, this fight isn't an aoe fest. DPS should be focus firing the adds down one at a time. Mercenaries first, then Priests, Then Mages, then Hunters, and Footmen last. The Footmen are pansies.
A final note, for the love of all that's holy, please don't try to tank in the center of the room, or line of sight WILL work against you. I had this idiot healer who wanted to stand ON the altar in the center of the room and expected me to run around and pick everything up. They dont make enough taunts to pick up every single one of them one by one while the healer stand in plain sight spamming Nourish and aggroing everything as soon as it spawns.