This is one tough giant, he knows how to stomp rogues and casters.
Earthquake: When Golemagg hits 10% HP he will start hitting everyone around him with earthquakes dealing quite a bit of damage.
Pyroblast: Golemagg will randomly shoot out large fireballs with an added 300 damage DoT.
Thrash: Double attack
Mangle: deals 80 damage
Pull the core rager guards off to the sides of the room, these are invulnerable so they need to be off-tanked till golemagg dies. Golemagg should be tanked pretty much where he's standing, no extra special pull strategy here.
Golemagg hits hard, and the beating on your tank just gets harder as the fight goes on. Once golemagg is under 20% your healer's will be hard pressed to keep your tank up, also your DPS needs a group of healers to keep them alive.
The adds are invulnerable and only die when golemagg goes down, keep a good off-tank and a healer or 2 on each of them. The good thing is this is a straight up melee fight so if you have enough DPS your good.