I think you will find issues when it comes down to rolling for gear. Some people will want you to only have one chance while others will think it's fine that you get one chance per character. A good example is when a very cool mount drops... do you get 3x chances or just one? Make sure whatever rule you are going with is known at the start of the raid!

I have to agree that shaman, druids and pallys might be a better raiding groups since they can bring more to the table.