I have healed few times as main healer using my thaum. Sure I have no emergency aoe heal like a conj but we beat the dungeon. I also have healed as Conj and avoided using medica as much as possible as I have seen many use it to much (almost as main heal) and gain aggro from tank. I mainly play caster DPS because I do know tanks and healers always get blamed if party dies. I will only blame them if I know it really is their fault. Like say tank pulled when healer says out of mana party dies. Um yeah but I also don't get mad I just say wait next time and laugh with them. I still won't play a tank but I do heal