He stalemated/defeated Jaina whilst disguised as a Vong. Not entirely positive what the circumstances were, but the text makes it seem as if she were amped.
Then there's Luke classifying him with high tier duelists like Katarn, and implying that he's better than Sith Bladesmaster Gaalan.
He also has been in a few duels besides that, I wouldn't discredit his merit as a swordsman, even if it wasn't his high point.
And of course, there's his Force feats--Which are pretty damn good.