Two of the same class is very easy to macro.
With RAF, you can easily get everything to 60th with time to spare.

I managed Shammies, Druids, Hunters and Priests (5x of each, all to 60th) in under a month.
The leveling pace is pretty insane to 60th.

That will get you two of everything you might like at 60th, and you can go from there.
It's a good idea to level anything you might want in the future, while its so fast/easy.
Once RAF is over, you should have max rested on a few combo's and can switch between them.

Play whatever is fun.