My primary issue is that in 5 games I never saw the fire tower. Also, the meta progression was rather filled out from the start, which I am sure is being done for testing/balancing, but it left me feeling slightly hollow.
As for critique, the first round needs rebalanced so a single tower can actually finish it without life loss. The fact that there is 0 way to ever finish it without losing life is really frustrating. It is a loss that is due to balance, not bad play or luck, so it definitely needs to be 100% every time.
What you have is solid, and definitely enjoyable. I am sure you have a lot more ideas for upgrades and stuff that fleshes out the "when this and that happen, you get extra tower cards" mechanic, which I love btw. There were several of those that did not appear to work though, sorry that I do not remember specifically which ones.