Best duo?

hi so me and my friend are planning on playing wotlk here on warmane and don't know which class to pick, well at least he doesn't.
im planning on being a shaman troll and what should he be, a warrior, a hunter?

im planning to be a healer, he's planning to be a tank.

should we switch to another race and let him be a paladin and me a priest instead of a shaman?

thanks

I'm gonna guess you plan to PvP. In Pvp, some comps are just not viable no matter what you do. If you wanna know wich ones are succesful I suggest you to check the PvP 2v2 ladder to get some ideas:
http://armory.warmane.com/ladder/2v2/Icecrown
http://armory.warmane.com/ladder/2v2/Blackrock

You said you would like to play a healer and a tank. A good heal and tanky dps would be the classic "Holy Paladin & Warrior"
Another option more fitting to what you wanted to play would be "Resto Shaman & Feral Druid" it's good but not perfect.

After all it's all depending on how serious you want to 2v2, if its just for fun or just basic gear you can pretty much play whatever, have fun :)