I found him quite useful in the non-standard sphere grid. The main point of which seems to be to mix and match jobs anyway, You can argue this isn't as good as the original specialization - and you'd be right, especially at high levels, but at least the game plays a bit differently.

In this scenario I often used Kimahri to pick up important abilities which you'd normally expect a character to have if they hadn't gone off on a diversionary route through the grid. Rather than not have them. Eg. Wakka has gone to get Haste and so delayed getting Sleep attack. Kimahri keeps on keeping on and gets it before you reach somewhere you really need it, like the mushroom rock road.