By that logic you wouldn't need different melee damage dealers, tanks, or healers, since that's what you can generalize their play style in the same way: tanks take damage, keep aggro and stay alive, melee DPS (the current version at least) do positional damage, and healers keep people alive. The whole point of having different jobs isn't just for the play style, but because people actually liked that job from a previous FF game, and desire to play as such. The whole reason that they cut out THF this time is because of lore, and I'm simply pointing out that there isn't really a need to.