The problem comes with Kimahri being moldable into any function that you desire. That also gives you 6 primary options, and any number of intermediate positions. More people can have fun with Kimahri if they would but a little bit of thought into what they want from a character that is virtually built from scratch. Do you like going pew pew with lazerbombs? Make a second Black Mage. Do you need someone who can use Armor Break without not being able to move again? Pull an Auron.

He is a Dragoon/Blue Mage. His first Overdrive is Jump. The very point of him being able to learn stuff from the enemy (and there's a bunch of stuff you can learn without going out of your way) is to make him more versatile. Who doesn't want a fighter with a multi-target healing spell?

Unfortunately, this potential is never fully realized on the first playthrough. You'll need to play FFX twice or so to really appreciate him, and unfortunately, there isn't much of an incentive to do so, unless you wanted to hear the Al Bhed translated THAT badly.

Technically, it isn't Blue Magic because he doesn't need to be hit and survive the blow to learn the magic. He gets it from Lancet.