mobs are hitting too hard on low level planets for heroic 4. Or the groups are too big.
Any details? What planet, heroic quest name, mob/player level/classes, etc.
In a heroic 4 on Coruscant as Sage healer, the only thing I found a bit annoying was that I ended up marking, crowd controlling and tanking on top of healing. But only once a DPS died as I noticed too late I was spamming myself instead of the correct target, thanks to the clumsy UI.