Phase 1: Tank

For Lord Marrowgar, 1 tank grabs aggro and pulls LM back to the circle in the center of the room and turns him away from the raid. The 2 off tanks stack on top of the tank to help soak Saber Lash, which splits 300% of Marrowgars weapon damage between 3 targets. Saber Lash will also place a debuff on the tanks that will exclude them from being targeted by Bone Spike. Melee moves in and attacks LM from behind and the ranged and healers spread out in a semi circle around the room.

Throughout the entire fight (Phase 1 and 2) LM will cast Cold flame at a random (currently presumed ranged) target. This is a slow moving line of blue flame that is fairly easy to avoid. Melee needs to be especially careful since Cold Flame will be spawning right on top of them.

Also throughout Phase 1, LM will cast Bone Spike Graveyard which will impale 3 raid members, excluding the tanks, on Bone Spikes. All DPS needs to quickly switch to the nearest Bone Spikes and burn them down, as they do 10% damage per second to the player caught in them.
Because of Bone Spikes, ranged should be careful not to stand to far off to the sides or behind everyone else so if they get Spiked they are both easy to see and other people don't have to run in order to DPS them.

Phase 1 last for 45 seconds on the pull, and then 1 minute 10 seconds after that. Most of the damage in this phase can be avoided or kept low if people avoid the Cold Flame and DPS down the Bone Spikes quickly.

Phase 2: Whirlwind

In Phase 2, LM will cast Bone Storm. Bone Storm has a 3 second cast so Melee should move away when he begins casting. Bone storm does ~ 5k damage when it hits a player and a continual 500 damage every few seconds to everyone. Since he also cast Cold Flame during this phase, it is best if everyone stays out of range to avoid getting hit, bleed ticks and Cold Flames damage all at the same time. Clothies especially should avoid him.

He will begin spinning and pick a random target and charge towards where they are standing. Once he reaches his target location he will cast 4 Cold Flames (one ahead, one behind, one left, and one right). He will spin there for a second or two then pick a new target, charge, and again cast Cold Flames in 4 directions. He will continue switching targets and charging until the 20 seconds of Bone Storm is finished.
It is possible for Ranged to DPS during Phase 2, but avoiding Bone Storm and Cold Flame are first priority. LM does not cast Bone Spikes during Bone Storm on Normal mode.

Once Bone Storm is finished, aggro is wiped and the Main Tank must re-establish aggro. LM is untauntable, so Tricks of the Trade and Misdirect should be reapplied and DPS should focus on getting out of the way and letting the tanks get him back into position before they begin DPS'ing. Anyone who is in front of the boss when he begins to cast Saber Lash on the tank is at serious risk of being 1 shot. It is safer to run through the flames to get out of the way than it is to stand in front of Marrowgar.