I play world pvp with a different mindset. Using world's advantage, using professions and playing with friends are game changers. Asking for best spec or class is not a right question for world pvp imo because this is not an instanced zone like bg's. I think it's about what makes the game fun for you in world pvp.
Owning people 1vs1 = Go for strongest duelist classes and specs
Big zerg fests = AoE spells, AoE heals
Ganking questing people as a party = Play what you find fun, there's is no best or worst