I used to play it a fair bit, but even after a fair number of hours I never got a solid hold of what made certain classes unique. All the game came down to for me, was "dodge the scary looking spells and attack as I can". I played a mobility based thief & a plague? based necro .. I just couldn't find anything solid to build with.
Aside from the obvious things behind capturing nodes.
Read as: Too used to WoW to make sense of it at the moment.
Edit: This is for the PvP! The storyline was beautifully done, but overly simple, I thought.