So, this might be a bit of thread necro-ing, but I figured I'd offer a quick pointer here.
D&D, as a DM-less system, is very hard to pull off. The lack of a central story such a dynamic creates makes the game super difficult to work properly.
I would say you should look into a game called Houses of the Blooded ( http://en.wikipedia.org/wiki/Houses_of_the_Blooded
It isn't a standard D&D game (it focuses more on courtly matters of the Ven race) and it plays almost exactly like what you want.
Players build a dice pool from their character and roll. The highest roll gets narration privileges, but players who "bet" dice can add more to the scene.
I've run a few games of it at cons, and it's really interesting. Sometimes I will end up sitting there for an entire four hour spot and I will say almost nothing. The players just take it and run with it.
Obviously, this is open to power gamers to completely run rampant through. But, as the book calls out, if you are worried that the people you are gaming with are you going to disrupt the game, or take fun away from other people, why are you playing with them in the first place?
PDFs of Houses of the Blooded aren't hard to find. But you should really consider looking into it. With a tweak or two, it might give you the kind of game you are looking for.