First question would be, when are people dying?
I've found that the more ranged on the fight the better. We usually run only 1 melee, 1 tank, 2 raid heals and a tank heals the rest are ranged (usually have a chicken and a hunter for the knockback and frost trap). tank on one side, all but the chicken on the other side, chicken is the pillar target. Chicken will stand out to get targetted, the pillar targets him he run back to melee ranged and kills the adds and knocking them back if they get too close. Hunter always lays the frost trap between where the pillar landed and the group. Chicken and the 1 melee will use the chains. Make sure that when magmaw comes up from the chains the tank gets into position before he comes up and that the tank taunts extremely quickly as magmaw will do 1 melee swing on the person with the highest threat/closest to him since he aggro dumps when he comes back up.