Mage +:

Warrior: Will suck, warrior is always eating since you have no heals, mage is squishy as the 2nd toon, but can't be the first due to having to micromanage the warrior abilities. Barely playable.

Shaman: Heals, nukes, rez... your best bet based on the options you listed, but not amazing. Definitely playable though.

Hunter: Mage can follow the hunter arround and nuke, but neither class really needs the other so not optimal. Playable, but you could do so much better.

Here's what you want if you want to rock as a mage and something else:

Priest: PW: Shield, heals, fear bomb, rez. buffs... yeah that's the win, being able to cast a shield and a HOT on the mage before it starts AE'ing a big group of mobs is the win, rez if the mage dies, heals, fears as a last resort, etc. #1 choice in my humble opinion.

Pally (prot spec): Can AE tank 5-6 mobs on his own very well... now add mage AE to double kill speed and cut downtime. Also heals, can rez, has nice buffs. #2 choice, since the mage will be the 2ndary character.