http://rockers.wikid.de/uploads/bwl_firemaw.jpg
(the illustration is not accruate about the size of firemaws hitbox (its actually bigger) and thus the offtank position. I will add a screenshot to make it clearer soon.)

Wing Buffet
Frontal AoE, reduces Aggro every 30 seconds (announced by CTRA)

Shadow Flame
Frontal AoE for 4000-5000 dmg (ignors all armor and resistances). Causes a strong DoT without Onyxia Scale Cloak.

Flame Buffet
Strong DoT Aura with LoS check plus non-dispellable debuff that increases fire damage taken

PLAN:

Positioning is critical and the fights is a wipe if the correct position of firemaw cannot be established very quick. Also everyone in raid has to understand how the line of sight works here. Understanding the illustration 100% is required for all players. Understanding the principle even more since it will be applied to all followup dragons in BWL.

Melee attacks until the flame buffet debuff stacks too high and they need healing. When that happens they move to the melee-safe-position and bandage up.

Ranged dps stays on the Line of sight to firemaw and cross it to the safezone when the debuff stacks too high... bandage

Healers position themselves so they only have LoS (Line of Sight) to the tank but not Firemaw. Avoiding the debuff (Flame buffet) on healers is critical.

Group 1 setup is MT1 + MT2 + MT3 + Warlock + Paladin. Group 2, 3 and 4 are heal teams A and B with pala + druid + 2x priest if possible. Healing only on Tanks, the fight is long, rotation is needed and DPS has to bandage.

Tanking Variant I
(Works for all 3 Dragons the same)

The dragons are tauntable. This opens up a beautiful way to keep him positioned and avoid all aggro-loss on the MT during Wing Buffet: 3 Seconds before the Wing Buffet, an offtank will taunt the Dragon while standing 90° off the Main Tank.

This forces the Wing Buffet on the Offtank who looses aggro back to the Main Tank once the effect of the taunt fades (3 sec). In other words: the offtank attempts to catch the bullet. It is important that the offtank's taunt is cast no longer than 3 seconds before the Wing Buffet. If 2 Offtanks are available they coordinate to cast the taunt staggered (Second taunt is cast about 2 seconds after the first) to cover any inaccuracies of the running timers.

Whoever is in the Wing Buffet's AoE gets knocked back 30-40 yards and has to run back immediately. Usually to the safe-position.

Required setup is three tanks, one main and two offtank. Both need to be warriors. They position themselves as indicated in the image above at a 90° angle. The offtanks stand in their safe-position most of the time to avoid the debuff. Once the Wing Buffet timer is running out, they move into their Taunt Position close enough to the Dragon to make sure that if aggro switches to the taunting tank, the dragon will not move, just turn to him (this is critical).

Tanking Variant II

This is an alternate pattern for Firemaw.

The Main Tank stands in the far left corner of the closed gate that leads to the lower trap-room and one offtank stands at the opposite side of the gate. Both are standing with their backs to the corner so a Wing Buffet wont knock them out of position.

The Offtank will build aggro together with the Main Tank and make sure he is at all time second on the Dragons hate-list. That way, whenever a Wing Buffet hits the Main Tank, the Offtank is there to briefly tank Firemaw until the Main Tank can taunt him back.

This is made possible because DPS is very slow in this fight and Healing of the Main Tank spread over many individual healers.

To make this work, a group of 2 priests has to be positioned accross the tank positions behind firemaw. There is a column to provide a LoS safezone for them. They just pop out of their safespot when the Wing Buffet timer is running out to burst heal the Offtank until the Main Tank has regained aggro.

For additional safety, a second Offtank can be added. They both build aggro and after each 2nd Wing Buffet one of them goes to the safespot to let the debuff wear out.