So for one, I think it's bad that healing items activate at the end of the turn, after or during creature attacks, but before weapons.
So, if you have 4 shards of divinity out, but take 2 damage during the opponent's turn and are knocked down to 98, you won't get elementary master if you win by attacking on your turn.
It really restricts getting element masteries. Is mastery supposed to be just about preventing all damage on the 2nd to last turn or having enough feral bonds out?
No... it's supposed to be about winning with 100 HP. But you can have 100 HP 19 out of 20 turns in the game, and have 6 shards of divinity out, and you won't get a mastery because the healing waits to kick in. But I think this deserves an EM just as much as having a feral bond out, or finishing off the opponent with a weapon instead of your creatures.
The same problem occurs with poison, if you have 2 poison counters, even if you are regenerating 20 HP a turn and take only 2 dmg per turn the whole game you don't get the Elemental Mastery... like that has anything to do with player skill?
Second gripe, the AI draws and plays cards quite slowly. I don't know if this is unavoidable due to computations, or by design. But it'd be nice if some aspects of the AI were speeded up, perhaps the animation when they draw the card, or whatever.