best PVP classFollow

Hey, I scanned and couldn't find this particular question anywhere, if I missed it I apologize.

I recently jumped on to Venekor with some friends to do a little PvP work. I'm normally a tank everywhere I go and so I rolled a Guardian to help by taking all the damage. Unfortunately I've quickly found out that tanks don't work at ALL in PvP situations. Most of the time I'm more of a liability than a help. So I was wondering:
What's the best class for an old tank-loving guy like me to play in PvP? In order to be effective do I really need to branch into the DPS world or is there a strategy that I can use to be an effective PvP tanker?

Thanks all

~H