I have leveled two mages(non-boxed) to 70 and I wouldn't recommend a 5 man mage team, it just limits you quite a bit. I would recommend using a pally in that group, cause a pally is a mage's best friend. Slapping down consecration so we can aoe our hearts out is priceless.

As a mage we are always on the verge of death and if you have everyone following you they will be a second slow and die many times. Then you have to corpse run... Add the Pally and you won't regret it. 4 x POM pyro is pretty sweet too.