Disregard Traviss when it comes to depictions of Jedi, and especially Jaina.
For some bizarre and completely unexplained reason, the Jedi whom pioneered most of the ways of combatting the Yuuzhan Vong suddenly was incapable of fighting an opponent that couldn't be sensed through the Force, and seemed to have inexplicably lost all her years of fighting skill.
To top it off, for reasons beyond comprehension she had Jaina go to the Mandalorians to learn how to defeat a Sith. Not her uncle Luke Skywalker, the greatest Jedi to have lived and most experienced member of the Jedi Order when it comes to combatting the Dark Side and its practitioners, but Space Vikings/Spartans/Hero Farmers who have an incredible record of failure against the Jedi Order in the past, and never even fought the Sith.
I've never understand why people take such a clear issue against Jaina going to Boba to learn new fighting techniques. I'm not the biggest Travis fan but I think it was at least well explained. Jaina may have developed countless fighting techniques over the years but much of it was learnt either fighting alongside her brother or in the time when they were still close and would both share details and spare against one another, which means that if she fights him in the style she usually would he's going to be prepared for it and as he's picked up a host of talents during his five year travels that she doesn't know he's going to have all the upper ground.
Yes she could go to Luke but as he's just fought with Jacen to a standstill with neither emerging the victor she clearly needs a different edge. All right Luke probably would have won his duel with Jacen were it not for Ben but that's not how the fight ended. Also she knows that Luke is having a hard time dealing with Mara's death and that adding her tutelage to his plate when he's struggling to lead the entire Order probably isn't the best thing to do.
You say she goes to farmers and space Vikings for training but that's not strictly true. She goes in search of Boba Fett who has a history of surviving against the odds and who has fought Jedi, is well trained in combat, was respected by Vader and can teach her a fighting style that she can mix with her Jedi abilities to be able to fight Jacen in ways he won't be expecting. Part of that ends up including her sparring with some of Fett's mandalorians and yes here they're strength is played up a little too much but that doesn't remove the entire basis for why she goes there in the first place.
There's a lot of LotF that is poorly written such as Han and Leia deciding Jacen is dead to them in pretty much every book only to decide it again in the following one, or Mandalorians who are much stronger than they should be (though at least that is slightly retconned when they have their asses handed to them in Invincible), but Jaina going to Fett for training that Jacen didn't expect made more sense than most of the plots since the NJO. It all boils down to: Jacen knows how she fights, she needs to mix a new different style with her Jedi abilities, Lukes a little busy and Fetts a man who tends to get the job done so might know a thing or two about fighting hard odds. Makes sense to me.