"The initial idea was to have cards with different effects..."
You really need that! My opinion is that there is nearly no strategy in the currrent gameplay because:
- The enemy always has better cards (more points) after a few battles, and that if a card has more point than what it faces, if all of its points are attack points, it always out-damage its opponent.
- There is no way for the player to plan-ahead: they cannot see what cards their future opoonents have or choose which opponent to fight next.
"The objective is to carefully choose your cards according to the opponent's cards."
The choice is simple school math: taking the expected net damage of a card by assuming equal probability of it facing any of the opposing cards, plus perhaps tkaing into account HP ratio.