Priest if you like to help other players. (Imo, that is pretty much it with Priests)
Their skills looks nice. :3
Their 3rdjob AoE can hit many targets, but slower cool-down. IMO, Priest is kind of hard to grind with because thier AoEs cool down time is too long. BUT - the new skills should arrive eventually -I don't know when- and apparently Priest is able to learn a skill that reduces the cool down of skills. So you might want to consider this too. :3
Wizards, depending on your elements may or may not be stronger than Priest.
As I know, if you are going Light + Fire + Elec.
Wiz are better, that is having access to good Aoe + 3 Damage over time skills + powerful single target + OK cool down + SoH. (If you are dark instead of light, you will get additional DoT and more powerful single target skills, but no SoH. But they grind just was well.)
The same with Water + Elec + Light/Dark. They have better combos because shard of glacier can reduce electric resist.
I'm not sure about other elements.