This is something that's bugged me a bit for a while now. First I'll say that I haven not ready ANY of the Legacy of the Force novels, so maybe I am missing something; all my info comes from Wookieepedia.
Now, is it just me, or is Darth Caedus/Jacen Solo given way too much credit when it comes to his abilities? From what I gather, Caedus is supposed to be the most powerful Jedi/Sith since Anakin Skywalker/Darth Vader. Yet, for some reason, his ability to win any fight seems to be inversely proportional to his alignment to the Dark Side. Think about it: as a Jedi, he beat back some of the greatest threats that the galaxy had known since the Empire. I read the last NJO book; I know he kicked @$$ then.
However, after he turned to the Dark Side, his track record becomes rather questionable...
Off the top of my head, following his turn to the Dark Side, Jacen wins only ONE Jedi vs. Sith battle. And he won it because he managed to trick Mara Jade, rather than any superior skill with a saber or the Force (granted, the way he tricked her makes it a legit move in my book). The only other time he seems to "win," the Jedi actually accomplished their objective, despite casualties. Other than those two fights, as far as I can tell, he gets beaten, if not pwned, in all other combat. I recall reading that he even loses limbs along the way!
So what happened? Does the Inverse Ninja Law not apply to books? Or did Caedus fail because he wasn't a real Sith Lord, and thus didn't achieve the necessary level of bad-@$$ to meet the Jedi evenly? I mean, for the second Sith to cause a Galactic Civil War in less than a century, at least Palpatine could take out 4 Jedi Masters in less than a minute. Perhaps Star Wars just ran out of good villains, since Palpatine already got the best villainous qualities...