Originally Posted by
winsock
Because:
1) a tank can kite to lower dmg and ultimately prevent a wipe... but will typically lower the outgoing DPS as well. You want to prevent the tank from deciding to kite
2) the overwhelming majority of the time, you can keep the tank at higher than a thread of hp, without impacting your DPS because you no longer need to be in cleric. There is no difference in HPS or DPS between [Holy, Holy, Cure II, Cure II, repeat] and [Holy, cure II, Holy, cure II, repeat] for example.