The primary loop is very well done, with some interesting strategic decisions. Lots of good game juice, with animation, icons, screen shake, sound effects, etc. Very cool music.
A few suggestions:
-The HUD should show how much damage/healing is being done
-The prompt should indicate which is "use" and which is "sacrifice"--it sounds silly, but I kept having to check, and would occasionally get it wrong.
-With some cards, there is no reason to ever use "sacrifice": e.g., with a LifeSteal 1. This cuts down the amount of strategy when dealt one of those cards.