I was surprised when I learned that
upgraded cards appear alongside the original cards. I feel like it causes some really weird issues that can be brutal in play. I don't feel like it was the card designers' intent that 4 mines existed in play at once. That can't be right, right? Some agents are really powerful alongside their original cards, like the Hireling alongside the Oathman.
Maybe this has already been discussed, but I didn't see anything at a glance in the forums.