Round 1:
Zannah vs. Bane goes either way, possibly favoring Bane in the first round in a shorter distance for him to employ lightning/superior force abilities to deflect Zannah or throw her off. He's the better duelist/force wielder and should win a majority over her as she's more or less useless as a duelist.
I don't care who wins between Malak or Traya, but he's the better duelist and that's an edge to him.
Between Legends Vader and Darth Caedus, Caedus is more skilled and should win a duel assuming Vader opts for a lightsaber match.
Round 2:
Zannah can probably hinder Bane or Malak with her mind spells, and while I doubt they'll oneshot them it should take them out long enough for Traya to kill them with her force abilities. Caedus likewise kills any of them (unless hindered by Vader's TK)/stomps Malak and Bane in any encounter