What class is should i play in WOW if im looking for the best dps?

I have a low lvl mage, I like him, but im doing terrible dps, no AOE spells and no Heirloom items. I know that a hunter is good dps low lvl, what about higher lvls? also pvp in consideration. I want to make an enhancement shaman, i saw that they do good dps on raids, is that only with heirloom items and how do you do so much dps on an enhancement shaman, or just what class would you suggest, thanks!