Enhance Shaman since day 1. Shaman all the way.
While I've spent more game time on my druid over the years than any other character, I've had my priest almost as long and she's been my main for the most recent chunk of time that I've played. I love to heal, I don't tank, and I don't mind dps but I'm not very good at it, so if I was going to choose anything it'd make sense that I'd go with the one class that has two different healing specs so that if one gets nerfed to the ground (which might very well happen soon) then I'll still have the other one to play.
Therefore, I chose priest in your poll.
I'll tell you what I wouldn't. Melee. They're all mind numbingly boring in MoP. Attack, gcd, attack, gcd, check secondary power, attack, gcd, finisher. Repeat.
Five Common MMO-C Misconceptions:
1. If I'm burnt out on WoW, the game must be less exciting than it was in BC/Wrath.
2. If Guild Wars 2 can do it, WoW should have done it 4-9 years ago.
3. Anything I don't get free is another way to milk the players for money.
4. "Don't hate me because I disagree" is a good way to shut down dissenting arguments.
5. GC is the root of all WoW's problems. Now that he is gone the game will be perfect again.
Easy poll for me. Only have my Warrior which i made 8 years ago. Never had any alts.