High Fire resistance fight, your MT should be fine with around 250-300 but the more the merrier.

Abilities

Inferno: Baron will stop moving or attacking and cast a AoE fire spell that deals quite a bit of damage, it pulses every second or so and should be avoided by the tank unless he has a lot of FR

Ignite Mana: This is a manaburn DoT that removes 400 mana and deals 400 damage a tick, this needs to be dispelled off mana using classes and your healers.

Living Bomb: Baron will cast this on random people, it has a timer that when it goes off explodes the player dealing 2-3k damage and flinging them in the air. Run away from the raid if you have this.

Pull

Most guilds will pull Baron Geddon back into Garr's room, this allows you to have a good fight center. Your raid should be positioned in a line a little ways away from the back wall. Geddon will be pulled into the center of the room.

Fight

The reason for the line formation is that whenever someone gets the bomb they will run back into the back wall and explode there. This allows you to easily avoid wiping from the bomb.

Your melee DPS will run in whenever Geddon isn't doing his AoE, if he starts have everyone move out except in some cases the MT. Geddon will eventually hit the MT with the bomb Debuff so be ready.

Other then the bomb this is a simple fight, good luck.