We tank him on the the side of the room where you enter (in the doorway you come in through). This way when the adds pop they are on teh opposite side of the room from the tank/dps and it makes it easier for us to snag em.

Positioning is:
caster dps off to one side of the ring (can target adds and boss without turning/moving from here).
MT on boss,
OT picks up adds - melee all burn adds, casters stay on boss unless something's going horribly wrong with adds.
Healers power through the Swarm, no one moves. Burning tank cooldowns right before swarm makes it much easier.