You're guys are right, my bad.
I didn't realize "_____ active skills recharge 3 gems faster" actually changed the numerical value on the back of the card (from 0/15 to 0/12, etc.). I thought it was always 12 and the perk just gave you 4 points for every 3 gems.
I was confused because I am used to fully charging Mythics using only 6 gems, which I now realize is because of the "All ____ gems get upgraded by one level." perk, Which every element has now except Earth. Apparently, if you only have level 0 gems to work with, you need all of them. But with all level 1 gems, then you only need half as many.
Still, it feels like Rockfall (Earth gems drop 2 times more often in any battle) isn't working like it should be. Only a half-dozen (or less) out of 42 total does not seem like "2 times more often" at all to me.