Why don't you just do what other games do?

DON'T TELL PEOPLE IF THE INSTANCE IS IN PROGRESS OR NOT.

If you check the mark to "allow in-progress groups" in every single game I've ever played, the game does not effin' tell you where the group is. You just zone in, and then the people in the group tell you where they are.

Don't separate the queues, because that'll just make queue times terrible for everyone.