I can see one MAJOR problem with tying attributes to class rank, that being that a rank 1 THM with 10 rank 50s will now be exactly the same as a new player on a rank 1 THM. They've gone from forcing you to rank all classes to making it so that no amount of ranks in other classes benefit you outside of the class itself.

I just hope by then that surplus is gone. Yeah, try to rank up that one class with 50% exp reduction now that no other class ranks are of any benefit to you outside of shared skills (which you won't have access to when playing a Job defined class, so enjoy).