In PVP, often the Classes are better than the jobs, dependingly. You see TONS of people going Marauder over Warrior in Front Lines, occasionally you see people going Archer over Bard, and Gladiator over Paladin. The point of classes is that they have more cross class abilities, and so the more jobs you level, the stronger classes become, similar to how Freelancer and Mime work in older Final Fantasies. Classes were also originally intended to be more for soloing and pvp while jobs were intended for PvE content and everything requiring a party.