The biggest reason why empire win most of the time over republic is not becaues the class are imbalanced, it's because the fact that a lot of empire skill cause internal and elemental damage which the Republic side can't or barely can mitigate.
Sure we have the Sage buff, but if you died then most likely 90% of the game you won't have the buff and thus have at best 11% reduction.
Sure we have some classes that can do internal damage or elemental but the damage the amount of damage these skill do and the frequency they can be used doesn't even compare with the two most played class on Empire side, Sorcerer and BH.
So until either gear have elemental/internal defense on them or they increase amount of buffs gained from armor to elemental/internal to 20%-25% (0.5% per level is not far fecth) base then the republic will always have an edge in combat. After all most of Empire skills gets reduced by 30-50% where the Empire in most cases their damage only gets reduced by 11%-21% if they lucky to have the buff.