The biggest problem isn't lvl 50's with experience in their class, it's the simple fact that a lvl 10 has 1 skill-bar of skills and a lvl 50 has 4 to choose from. For example a lvl 10 sith sorcerer wouldn't have the crushing darkness DOT or Static Barrier. And those 2 are only a few lvl's higher but they make a huge difference in pvp, a lvl 50 has lots more skills.
Other then the skills ... the talent points make an immense difference.