PvP DPS: Extremely fun, granted you can keep track of your blink / charge(s) / cc immunity cc. Getting crits are extremely rewarding granted you again can keep track of your stacks + condemnation. Aside from a strict DPS perspective you do get a lot of utility, such as single target + AoE Taunt which is extremely useful in protecting the healer at your point, negating threat to a squishy dps, tie in a couple of blinds, hooks and roots and you have a very fun, interactive and engaging class hat prevents pvp from getting stale.
PvE DPS: Can't comment, never used it but it seems to be quite decent in non-challenging PvE scenarios, granted being a melee dps in hard raids, high lvl compasses without excessive knowledge of mechanics and perfect reaction you are basically doomed from the start (But of course cash shop items help to relieve some of these scenarios). But from an over arching standpoint melee dps in pve are a second hand choice, apart from cleric.
Tank: Pretty straightforward spec, definitely a good pick for any situation. I find it to be excessively boring and slow paced and do my best to avoid tanking, but don't let this deter you if you are interested in the class.
Definitely check out some of the addons, such as Paladin Helper, Barrier Manager / Anatomy self defense as I have found these to make the class even easier to play and takes away a few more things to constantly monitor such as incineration stacks, when your barriers have more than x amount stored in them etc.
Unfortunately I still pretty shit at the class, but if you have any questions on introductory stuff like generic stats / builds / rotations etc. I will do my best to help out.
Just pm me in game preferably, New frontier: League: Korsakoff