As lots of people will say play what is fun.

These are my Current 80s

Account 1: DK
Account 2: Priest/Shaman
Account 3: Mage/Shaman
Account 4: Mage/Shaman
Account 5: Hunter/Shaman

I have tried all combinations of the above and found I really like.

DK, Preist, Shaman x 3

I find that with a good inn location, Argent Stand minutes away from easy heroics, ToC, and Dalaran, and the 30 minute Hearthstones getting places is never hard. Food/Water really is not a big deal I use freerefills to keep my guys stocked up automatically.

Buffs are awesome with fort, spirit, fear ward, horn of winter, drums, and totems.

In the end though do what you find challenging/fun.