well reaching duelist/gladiator levels in arena boils down to primarily knowing your opponents inside and out and how to counter every thing they are capable of throwing at you
Mages are in a very good place right now(some argue too good but that argument doesn't belong here)
To truly grasp the mechanics of arena, you need to hit the books and learn EVERY class and possible comps they use
As it has been mentions plenty of times, hit up arenajunkies and maybe even EJ and look at the basic overview of every classes spec and their stratagies