I've yet too run into a bad healer,but I always run into horrible dps,or a dumb tank.
This demonology warlock was pulling 1.2k DPS in heroic Pit of Saron,they were using a imp yet they had a point in felguard,then the next I got into another heroic pit of saron,we got too ick,krick and this hunter was standing in all the toxic waste,wouldn't run when ick pursuited him.