Anything you want to play will work out, especially for leveling and world play.

PvP will require a bit more thought, if you want to be successful at the higher ends of play - particularly arena.
Similarly, PvE content such as heroics will require some kind of a tanking toon, some form of healing and enough dps to down the mobs before you run out of health/mana.

Almost any combination can level up.
So the question is to decide on something which you find to be enjoyable.

Not sure how many accounts you are running at once, or what your eventual goals for the team will be.