Paladins are normally underestimated in PvP. As a Paladin, you wont nuke them dead in 2 seconds, but you wont be nuked dead in 2 seconds by others either. What you have to be careful of is Hunters that use concussive shot and Mages that freeze and chill you. This is dangerous, as you cant shoot. By using a 2h weapon in PvP and with the shields and heals, Paladins are one of the classes that last longest in PvP. As a Paladin, we have managed to kill 3 equal leveled players alone in PvP by killing one, stunning, healing, shield, heal and kill and so on. Trying to do it, you will at least not waste too much cheap mesos.
Paladins should not be tanks in instance. And not heal until high levels, as a Paladin who wants to level wont have holy talents. In addition, a normal Paladin below level 60 usually wont have all too high intellect, meaning low mana.