Tera pvp is spited in different disciplines, so its more a question about "what kind of pvp" you want to practice.
We have the categories Mass pvp (100-20 players) with objects, Raid PvP (20-7) with objects, Group PvP (7-3) and at last 1 vs 1. These are subcategories for OwPvP and BG pvp.
As you see the higher the scale of players is the higher benefit it is to be a Ranged or strong front line class or healer. (like Gunner, Archer, Lancer etc)
For lower scale of players melees start s to be more interesting and rewarding (like Warrior, Slayer, Ninja)
The main reason i listed this up is that some classes are better in some situation against another classes. Overall you should consist that not every class is simple to play and need practice to achieve his full potential. (example would be lancer)
At the end its more interesting to pick what you like to play.