Shamans are probably the easiest kill in the game and the weakest PvP class. Enhance is the strongest, arguably, of the specs for PvP once you get your wolves. In fact, in the 40s and 50s, its tough to beat, but loses power higher up. I don't know what lvl you are but most shammies cant survive a ganking. Resto is tough to kill but has only one insta-heal and a dispellable bubble, so it's not exactly an i-win button.