I had a lot of problems with this guy as well. I am using 5 clerics 1 tank, 1 healer, and 3 dps. First of all I had a lot of trouble with this fight until I was a few levels higher than the minimum to enter the dungeon (not sure what that is). Basically I put everyone on follow and just ran around the room in a circle killing the adds and staying out of the fire. When the boss lands I would run the group to the boss and break auto follow. When the fire drops on the group I would use straif to move out of it. When the boss teleports I would put everyone on auto follow and repeat. You also want to make sure that you interrupt the Cinder burst ( I think that is what its called) because that will do a ton of damage to a group member.