I don't find them that hard to keep track of; with a couple exceptions the name of the career can generally tell you which book it's from.
I'm also the referee, so no careers get through without my okay. I'm not sure what use an index would be. I don't consider any of the career paths "overpowered", so I can't see anybody using an index to figure out which book they should buy for one class. That just seems like a waste of money. (Don't get me wrong, I love the career books, but there's so much more useful information in them!)
To each their own, I can compile a list when life stops kicking me if people want.