It says PvP because you can get killed by the another faction in any moment (except if you're in a santuary), in a PvE server both players have to do hostile actions to have the chance to kill themselves.
At this moment a lot of spells are broken, but the warrior is really playable, easy to use and good damage.
If you're looking for a caster DPS go Balance druid or Fire Mage.
And if you're looking for a heal go resto druid or mistweaver monk.
Hope it helps, and again, if you have another question feel free to ask.