Alpha DOOmega and Pyromancer is the best for PVP. Elemental Dracomancer is good, but is not as good as Alpha DOOmega or Pyromancer.
With Alpha DOOmega PVP is really simple. All you do is use the 3rd Skill (Stun) followed by the 4th Skill (Guaranteed Crit). If your enemy still isn't dead, spam the 1st Skill until your opponent is dead.
Using Pyromancer, use the 3rd Skill first (preferably right before the match starts) than followed by the 1st Skill than the 4th Skill. The 3rd Skill helps reduce incoming damage and the 1st Skill + the 4th Skill results in massive damage.
Remember to use all luck for these classes. Good luck!