I'm not done with my first playthrough and I'm not sure I'm going to finish it. While there are some interesting concept and as OP said, the design is fantastic, some cards are all over the place. It explored many concepts and it makes it tedious to play. I pretty much too any card just to explore and found myself having no challenge at all, on my first playthrough.

My biggest complaint is Pattern Shift... this card is common but it's one of the most OP card in there. When you know the game, it breaks pretty much any boss or elite monster, you can skip Nob's enrage, Hexafire guy's fire rush (x6 attack), Snecko's confuse(if you don't want it) or any scale up moves that enemies can do. On top of it, the card is self-retaining so you always have it in a non-bloated deck when you need it and on top of that it does not exhaust. Not only it should be rare, but it should exhaust and the self retaining should be added on upgrade. Needless to say this character is for experienced player, but if a player is not sure about an enemy's next intent, you can use the card to know without expanding it. This card is just the definition of OP.

a bug? : The Fallback and Spring forward card didnt seem to work as intended. When I used Fallback, the card got exhausted without anything mentioning this on the card.

Here's something I liked :
I liked the Exo-coating card... I thought the base game lacked some cards capitalizing on the Plated Armor's mechanic and the switching cards were a good idea for those. I'd like to see that "build" explored further.

It might just be me, but the combo making wasn't fun to think through, it was way to tedious to try to pull off and even then I didn't feel like I needed to, because I never failed to have enough block to soak the damage without putting much thought into it.

The Powers (Replicas) is a cool idea but at the same time it felt like it didn't fit the character who seems to revolve around Time. Fibonacci's card, while interesting, why is that there?

It's the first mod I tried. I think it was well implemented and has many good ideas. I don't think I'll replay it but I hope some of the ideas can be taken from this and a more refined character can come out of it.