You should rather not not focus on on playing the top single target dps class, but on playing the class class that fits your playstyle most. Some classes are melee, some ranged, some are easy to play (most are
), some require more micro management, some do do more aoe, some more single target dps, some are tougher, others make more damage.
As you see, it all depends on your personal playstyle how much damage you do (naturally limited by the class skills itself). I have seen warriors that sucked hard, but when they switched to mage, they suddenly were top dps.
I hope you find your class