9's probably pretty hard, that has the best shot of beating him.
Boss is an odd mix. A Droideka is dangerous, but ranged dangerous. Kenobi and the Magnadroid are melee dangerous. And it's only AotC Kenobi... who, while still dangerous, is definitely at a level where he needs help to take on a top council fighter like Nihl. I don't think a lone magnadroid is enough (especially considering force can take it out easily), the Droideka might be, but can a Droideka's blasters really support duelists very well? So, I'm going to toss in a 'dunno' on that one.