Thanks for the honest feedback! Are you able to be more specific about what was frustrating you? It'd be good to know what people struggled with if we decide to expand on the game.
There is indeed a good basis. I would have liked the bot to make "logical" choices between cards. For example, if a card has an extra effect on the first turn, the bot plays it.
The player must be able to anticipate his bot's actions at a minimum. Randomness shouldn't be too frustrating.
But the enemy robot could play in a non-optimal way, which would be a way of dosing the difficulty.
You're talking about opening gambit - Those are valid points. It would have been nice if we were able to get some basic AI into the game, but when we were getting to the point of designing the boss fights we knew we weren't going to get there. So we built these challenges assuming the player would use card costs to limit what can be played from hand. We definitely could have been clearer that the cards are played randomly (assuming the card's cost can be paid), so I can definitely see how the hero making bad moves could be frustrating. That's legitimately helpful feedback!
If you feel like giving the game another shot I'd love to know if thinking about using card costs to control what can be played from hand helps make the game more enjoyable for you. No worries either way, and thanks again!