I don't know. My diorite/raxa drop rate has increased considerably since 90 on aura statues. These days I don't go longer than a hour or so to get a diorite to drop. Often it's within 30 minutes. Raxa has been dropping considerably more often too, considering I never saw a single one drop back at 75. Water drop rate went up, too. I almost want to say that it's possibly the drop rates were increased along with other increases in sky, but that doesn't explain away the unrelated raxa drops.
I do know that I haven't gotten a single of anything to drop without procs.