I finished the game, it was pretty fun. I was hoping it'd last a little longer to better customize the deck.
I think getting the same items (equipment) should make them stack, otherwise it's probably always best to remove/duplicate cards. I liked that particular mechanic, by the way.
The double attack enemy x2 was the hardest battle for me. It was insta-defeat twice. The only times I lost party members were those two times, losing the leaders.