Which classes do you specifically need?

There are certain classes that I really like having at least one of regardless of sub-spec or raid size. For example I want at least one each of the following:

Paladin – At least Blessing of Kings and a Paladin Aura active.

Druid – Provide the Mark of the Wild buff and a Battle Rez and Innervate for emergencies.

Priest – You always need Fortitude active to supply more health for your tanks.

Shaman – Heroism / Bloodlust, need I say more about how to make easy Ever Quest 2 Gold?

Between avoiding Lava Walls, and killing Fire Elementals all DPS should be on Sartharion. Getting up as many DoTs as possible makes this fight go much faster. Avoid the Lava Waves, kill off the Fire Elementals regularly, and keep Sartharion from turning to the raid and you will easily win this boss fight.