IMO it should be a class that can create advantages. Paladin FC is very good at maintaining ground but not really gaining ground. I don't know a ton about being on O as paladin but it's definitely really good at just running around and not dying with the flag.
Potential for mage is completely determined by your team IMO. Mages are the kings of manipulating the enemy team but if your team doesn't make plays off of that then mage is much less effective due to low damage.
I think a good rogue or a good hunter can hardcore influence a game singlehandedly regardless of what your team is doing. Warrior can too in the right hands. All of these classes have good utility, are annoying to kill, and range from high to very high damage, rogue obviously being the highest.