I've seen numbers from raid instances that show us (Hunters) doing the second highest damage over the course of a whole raid instance. For example, on a given outing in Molten Core, a Rogue might do about 1,300,000 damage over a section of the raid. Over the same section, a Hunter can get to around 1,200,000 depending on gear and mana use. Mages fall way behind to 800,000-900,000, because they're only good for burst damage - their mana pools run out in a minute or two on a ten minute fight. I can't seem to find the links I was looking at last night, but I'll try and dig them up later.