I think a lot depends on class and also on what other gear and enchants the person has. Say a warrior in full donator with Mongoose and Crusader and maxed attk/crit gear would be a pure dps machine. However you can get T5 and all the enchants as well as player made gems and meta gems and be very competitive.
Most of pvp comes down to skill levels and how often people have done pvp in the past. I know myself that I have done very little pvp in
WOW. I loved the FPS Tribes for pvp action but never got into the
wow version. I have to say that Donators being called a cheater is wrong. If you take advantage of all there is to offer you are not cheating. Perhaps the comment of having donators allowed on team events only and not 1v1 is a good idea.
Oh well kill hard and loot big I say