Make Diamonds Rarer (also for emeralds if needed)

This isn't really a bug, but rather, a suggestion. I personally think that it is much easier to find diamonds now than it was prior to the cave update. Sure, the plethora of mobs spawning in those caves will be kinda difficult to deal with, but that's really a one-time thing. (unless you don't put torches down.) Now, of course, mods are going to make it harder, but for vanilla feel it kind of takes away the difficulty of finding them.