I'm sure that prominent Sith will make appearances in the comics.
However, Haazen turned out to be one of my favorite Dark Side villains. The man managed to manipulate the Jedi Order into turning on itself briefly, and from the inside. Kun did it from without, and most of the other Sith just through their minions at the Jedi in hopes of destroying them all. I'm a sucker for manipulation.
I do think they intentionally goaded us into thinking that Lady Draay would be Darth Traya and that Haazen would be Darth Sion, of course, but it all came off well.
That would be really cool if they did another series focusing more on the Mandalorian Wars.
Give it the same kind of treatment as the Clone Wars. Lots of details and specific battles. Plenty of story material there they could use without involving Revan (if they have issues with that.)
Malak seems like the chief spokesperson anyways.