I played it and I'm not a big fan. I know it's supposed to be based off magma chamber but the game is really boring. For the 2v2, it's the first to a tower, a kill on each hero or 100 CS. Really lame.
It's a game mode made for people to go like "OH BRA 1V1 ME BRA", but it's not very fun to me.
Anyway. In terms of duelists right now, Draven is up there. It's hard to really pick one or two champions because there are always some champs that work better against others, but a skilled Draven is one of the meanest 1v1's in the game. Leblanc is up there as well.