Fascinating how you can turn every post into a "can pallies actually dps and tank" discussion.
At least be honest to the guy and tell him that only like every 20th guild takes nonhealer pallies, shamans, druids and that they are mostly low-tier (doesnt have to be a bad thing to be casual).
I guess OP just wants some dps comparison to then roll the class with the highest average. All healers are needed and have their specific roles to fulfill, hence all equally viable and whatever others say, no hps isnt a thing in vanilla .
Prot the only tanking class (sorry).
Dps is already mentionned, hunter will most likely be shit soon, priest = only 1 per guild.
Warlock, Mage (frost in mc and bwl later on fire in zg, aq and naxx), Fury, rogue all on the safe side in any content but the 2latest become less melee friendly with boss mechanics overall. Also 95% of all players have l2p issue, if you want to be a good dps just play the class you want to learn and read stuff about in-depth, most players dont do dps with any gear and any spec.