EDIT: I listed how easy it would be on a scale of 1-10, 1=hardest, 10=easiest

2/10 Magex4, priestx1
1/10 Magex4 warrx1
7/10 Lockx4 priestx1
7/10 Lockx2 magex2 priestx1
8/10 Shamanx5

Leveling 5 characters together without running instances sounds like torture to me and you will really struggle in instances without some kind of tank and some kind of healer. Not saying it is impossible, it will just be really hard.

1x Pally and 4x Shaman seems to be the current fad and gives you a tank with lots of healing and dps and 4 characters are the same which should make it easy enough to macro.

Hmmm....this got me thinking. Anyone have a bear, 3x boomkin and a tree?