As some have already alluded to in the thread, class mission bonus experience will have no effect on Makeb. Technically speaking, the missions you will be going through in Rise of the Hutt Cartel are planetary arcs, etc. and are not classified as class missions.
So in other words, don't buy these unlocks if you haven't already, since they've already told us there will never be more class missions. Especially not with Cartel Coins, they're not worth it.