As Disc, I've yet to actually heal in a dungeon. I can just spam Smite / Holy Fire / Penance / DoTs on the mobs/bosses, and the smart heal DPS provides is enough to keep everyone up - at the same time I'm actually doing competitive DPS, sometimes even topping.
What. Please tell me I can do this at 90 as well in heroics / HC Scenarios. It's just silly. I love it.