Color me as one of the folks who don't care about team deathmatch or dueling in
Diablo III. I only played co-op in the second game and that's how I'm going about in the third game as well even when they release it. But, I know folks are clamoring for it and you might get team deathmatch, eventually.
The folks at Blizzard
are going back to the drawing board on team deathmatch as it's not where they want it to be. I would think it would be really tough to try and balance everything out considering the game's really made for co-oping with a few friends, rather than going against them. I know a few wizard configurations and maybe witch doctors that could probably dominate a deathmatch type scenario, but I guess that remains to be seen. So, you're going to have to wait a bit longer for team deathmatch as Blizzard goes about trying to think of a way to make it compelling.
Dueling, though, seems to be coming soon and when I say soon I mean patch 1.07 early next year. We'll have to wait and see if it does get released, but Blizzard's aiming for that version to let you guys duel it out.