Except that you'd have to clear the instance to get the bonus. So if healers don't heal boot them because you're not clearing the instance.
Or make it a hp healed + dps done reward. Calculate how much unavoidable damage there is in an instance, multiply by 1.5 or something because invariably people take more than just unavoidable damage, then set a low DPS threshold in addition to that. There, healers who wanna heal can, but they don't get the bonus. Healers who do their job and also DPS get a bonus. Done. Signed, sealed delivered.
