Far more personal opinion kind of thing than anything else. xD From my perspective, only considering WoE [ I'm not very experienced with PVP ]:
1. SinX. They slide through most of the careless defenses, can kill most players pretty bloody quickly, have an actually decent HP mod, and other things. Ideal for quick elimination of small defending groups, and taking the Emp.
Their only down point is they aren't really designed for defensive game play.
2. Lord Knights. Peco pecos make them faster, and the fact that they're large rather than medium reduces the damage from your typical WoE weapons, unless they're actually intelligent enough to keep another weapon ready for them. They can break an emp pretty quickly, have an nice HP mod, and are pretty good destroyers of players.
If it wasn't for the fact that SinX kill a hell of a lot faster, Lord Knights would be first.
3. Professors. The bane of nearly everything if you can find someone who is actually bloody competent with them. Safety Walls = no damage for ten hits, thus saving people from one hit deaths from attacks like Sonic Blow or Guillotine Fist. The Endow + elemental combination = no damage as well. Their endows make them friends of anyone fighting against a multi-armor holding player, deluge is a friend of any Wizard with waterball, and dispell make them, without a doubt, the most irritating class in the game to deal with. The combination of Spiderweb + Stone Curse + Mind Breaker + Double Casting + Volcano + Fire Bolt = a shot that will put any enemy pretty close to death, if you can actually pull it off.
The only problem is that a GTB make them suddenly damn near useless, they can't attack the emp, and they're often targeted first. Since their HP mod sucks, it doesn't take much to take the down.
