Wouldn't it be a good idea to reopen these two areas in the next patch? It's impossible to collect all cards if you visited them already. I'm almost at the end of the game with 31 hours playtime and I just discovered I have to replay the entire campaign to get the last four achievements.
Not only 'Gotta Have 'Em All' and 'Obsessive Compulsive' are impossible to achieve now, also 'Hardest Deck' and 'Minigamer' because Teague uses the four cards I hadn't picked up and uses those against me.
Besides, the replay-value would be a lot bigger if all areas remained open and populated (like in Fallout or Borderlands).

You don't need to beat "hardest deck" to get minigamer. you just have to win at each game.

Yes, leaving them open would be cool I think too.

Actually, I managed to beat Teague's hardest deck (I believe by luck of draw) with only around 33 of the cards. It can be done, just got luck of the draw and good deck building to get that one

I too, however, would like to see it so that the cards are possible to get even if you have only got the last mission to complete.

I beat Teague on my first try against her. I got lucky though.