In a proper party a healer should have plenty of time to throw up Cleric Stance and nuke with some Stone II's. So in a sense White Mages should be playing as a ghetto Black mage. However a Good White Mage will be ready to switch in and out of cleric stance at a moments notice to maximus the speed of the run and keep the tank and DPS safe. I switch Cleric Stance on and off close to 100 times in some runs.