Also I think multiple DPSers would have a better chance to help the raid because they do the same thing(especially if you can get them on the top of the dps list). My next group I am leveling is going to be 2 shadow priests. They do the same thing and have a lot of utility, mana regen, healing. I think they have a more viable chance in endgame raids than mixed heal/tank/dps groups.

I think that most people don't want 1 person's trial and error to waste 20 other people's time. You just have to prove yourself in Kara, then work up from there.