I'd suggest playing a tank if you plan to 5-box tank/healer/3 DPS, as most people seem to drive their team from the tank. Paladin is a good one to start with. Alternatively, a high-level BM Hunter with AE-focused talents would rip through any lower level content.

I'd also suggest if this is your first time playing WoW that you don't use RAF. There is a lot of good content at lower levels and you level at a decent rate just by doing instances; even faster with heirlooms which a new player could fund with a single WoW token purchase. You'll also learn to play the game. Legion gets you the opportunity to grant level 100 to one character per account if you want to skip to the end-game.