My suggestion is simply make 1 of every class, and play all of them. There isn't much to look forward to these days as far as end game content, so playing an alt at any level is ok. Try leveling through battlegrounds with a hunter in full heirlooms, you'll be giggling in every match.
Haven't played my Shaman for a few weeks, just burnt out I think but can't bring myself to reroll fully because it was my first character and has been my main since the tail end of BC.
As of right now in MoP I have Hunter, DK, Rogue, Monk, and Mage at 90 while the others are still 85
So you could say I know every class pretty well. I don't like ANY of them for real except Hunter & DK at this point....
(I mostly PVP, anything is fine though if you're a PVE'r I guess)
still not completed all the rep grinds on my main so barely have time to look at an alt. the thought of doing it all again even with the bonus makes me shudder.