The difficulty is definitely something that is constantly being fine-tuned, so it's possible some of the fights will get tweaked in the future. Admittedly, a lot of the key opponents tend to have pretty strong unique cards as a way to compensate for the CPU not being good enough to make more interesting plays.
Though, to make it clear: it is a very deliberate choice to have fights - especially notable ones like Bucky - feel like they could go either way. Because the game keeps on going even if you lose, the difficulty is designed in a way where you're not expected to win every fight - the losses can be more narratively interesting, and in some cases even give rewards different from the winning branch.
Based on the remark about "invalidating your win with Bucky", it sounds like part of what's causing your frustration is the expectation that you should be winning every fight, and that losing is bad - which is fair if that's what you're looking for in a game, but it isn't really what this one's trying to do.
I am genuinely interested in playing around with the medium and making a proper game - if all I wanted to do was be horny, there are many other much easier ways to do that that don't involve the amount of workload that game development requires.