This is a copy of the guide my husband (Prot Pally) stuck up on the Guild Website. It does not take account of the latest 'Marrowgar is no longer taunt-immune' hotfix, and in the main is a copy of the tactic available on WoWWiki. However this is not why it's here. The Graphics are. In my husband's world, he is a nine year old in a tank and I am a machine-gun wielding Gopher. Go figure... :D
Here's a thing about Lord Marrowgar:
•Lord Marrowgar will now do significantly less melee damage in both the 10 player normal and 10 player heroic difficulty.
So, anyway, tactics....
Lord Marrowgar is a two-phase repeating fight.
Phase One is the Bone Graveyard phase where the tanks stand on one side of Marrowgar and the DPS and healers stand on the other.
Phase Two is the Bone Storm phase and consists of the duration of Marrowgar's Bone Storm.
The transition from Phase Two back to Phase One is what will kill most raids. uh huh
Three healers are useful to handle tank healing when a healer gets hit with a spike.
In the Bone Graveyard phase the raid wants to stay close to each other with the melee in the middle, the ranged on the sides, and the healers in-between the melee and the ranged. The healers need to be in range of the tanks, but farther from the boss than the melee. This setup specifically allows the melee to swap to any Bone Spikes that hit raid members near them allowing the spikes to be nuked inside 2 gcds. By doing this you minimise the damage taken by the spike target, maximise the raid's time on the boss, and minimise any interruption to the melees' rotations by target switching.
Here's P1 diagrammatically:
Regardless of how you handle the spikes, the raid needs to spread out as soon as the third spike is killed because the boss is about to transition to phase two.
In the Bone Storm phase of 10-normal, the raid wants to avoid the Cold Fire at all costs. The damage from the Bone Storm is negligible if you have competent raid healing and avoid standing directly under the boss when possible. The damage from Bone Storm is AoE, so abilities like a rogue's Feint will work to full effect.
In short, don't stand in fire.
Here's P2 diagrammatically. Maybe a bit spread out, but it's not that big a room. Try not to overstretch the healers. Don't stand in blue stuffs.
The transition from Phase Two back to Phase One is the difficult part, as he does a complete aggro wipe. To transition safely (for those of us who aren't farming heroic ToC) the raid, except for the tanks, need to stop DPS on the boss when he hits his fourth target's location. Once the fourth stationary spin is complete he'll wipe aggro and the tanks can pick him up.
Tanks will stand between the boss the the outside wall, wherever is convenient. Mark the tanks, watch where they're going, and re-form the T-shape of melee/healers/ranged behind the boss.
Here's the Second P1 diagrammatically:
Phase Two and Misdirects
The transition and Misdirect love each other. They really do. Tricks of the Trade on the other hand will get a rogue killed because before the boss aggroes your Tricks target, he'll one-shot you with a 30k Saber Lash.
I'll let you know if it all works out later... :D