Good point. Yes, choke points can work both ways. Especially if enemies can buff their front-liners while out of sight of the party. That can be a nasty trick
Make the characters start looking for the doors to get around back of the enemies, I say!!!
This just reminded me, I had a hilarious fight scene once where half the party goes to each door opposite each other to bust in and attack the throne room. Good plan, but it turns out that those two doors did not in fact go to the same room as each other. They ended up starting two encounters at once, both with only half the party. They were fighting the king in his throne room at the same time as provoking the archbishop in his vestry.
It made for some hard GMing, as although punishing them for this was very funny for us all, I did not want to wipe the party given that they had no way of knowing that those doors did not go to the same room.