I have noticed that when you are in the entrance to a dungeon or a boss you cannot get off of the entrance once you have hit "x". My suggestion (well, my brother's, but I agree) is to add something that allows you to hop off the entrance, even after you have hit "x". Though, there may be an exit that I am not aware of?
I think this would be useful for a few reasons.
Sometimes people have second thoughts about entering when they realize they don't have enough health, or something of that nature.
If they would like to solo a boss or dungeon and someone else joins them it can be a bit frustrating. Sometimes I myself would like to solo something, and then I am stuck with another player.
If you were waiting for someone to join, but they were hopping on a bit too late, this could be helpful to help you wait for them.
So there is my suggestion. Feedback would be great, and if this is already able to be done, could someone let me know how?