I'm a little scared by some of the reactions here.
In short it's pretty much this: group with the people that have the same idea of fun as you have. I would totally love a group with uncommon specs if those people are having a ton of fun playing those specs. We would just play the game to play the game, not to be server first, but everyone would have fun and try real hard to prove that it is possible to have fun and down bosses at the same time.
It wouldn't be as fast or as efficient, but the sheer pleasure of being with like minded people would be the best reward to me.
Then again, I also wouldn't stop others from getting an optimalized run if that's what's important to them. I simply wouldn't join their group, as it would be disastrous for both sides.
Considering most groups want to rush through you might indeed have a hard time pugging. Then again, playing a spec against your will is not my idea of 'gaming'. I'd rather not have a run then something I don't enjoy.
edit:
You can play optimalized all you want but if you don't get this:
https://www.youtube.com/watch?v=gcA6y7sxKcAThe raid will still blow up

)))
Orthodoxy wrote:Nothing you said justifies bringing subpar specs to raid over the tons of people willing to roll with viable ones. Can Naxx be done with elemental shamans and ret Paladins? Possibly. The question isn't can it be done, the question is why should it. None of the walls of text you have posted addresses this question.
Urgh, not gonna look up the spongebob FUN song but you know... the answer to your question is "because FUN".