In the Snow Dragon battle, there are some issues.
The Earth Aztecs set ability Rockfall (Earth gems drop 2 times more often in any battle) does not appear to be working. After a near full board clear by myself or the boss, and seeing only 4-6 earth gems (and they're nowhere near each other) on the board doesn't seem like it's working.
The Earth Fairy Tale set ability Magic Dust (Earth active skills recharge 3 gems faster) is definitely not working. A Mythic skill (12) should fully charge with only 9 earth gems. It doesn't.
Killing these guys above level 10 or 11 absolutely requires you to charge all five abilities on every even numbered turn, and use all five abilities on every odd numbered turn.
I wouldn't be a bit surprised if Country Cousins' Mother Nature (-80% extra damage from gems to the water cards) and Whores of Babylon's Power of Earth (+100% extra damage from gems to the earth cards) weren't working either, but I have no way of definitively testing those.