Where is the worry for DPS that

Where is the worry for DPS that uses the wrong spell? Why don't they run oom and not be able to dps? Oh, buy wow gold well that's easy. You wouldn't be able to kill the boss if all the dps ran out of mana! Mana should only be an issue for healers, right? Who cares if you can't heal through the damage because someone stood in fire? According to Blizzard, at least what I can infer from what they're attempting to do with healing, healers are only there to heal the absolutely unavoidable damage and keep players just alive enough to not die from the next hit. WHAT FUN. If anything goes wrong, be prepared to use the spells you shouldn't use because they're a waste of mana and someone screwed up! Stupid dps! Stupid healer!

Only healers should have to worry about conserving resources. I watch dps blow all their CDs when attacking me, and I can stay a live through a lot of it. But why don't I get to watch their mana run out? Mine sure does simply trying to stay alive.