This kind of option does seem ideal, but unfortunately as soon as it becomes available your going to find out how useless it is. DDs think your waiting a long time now? well step in line with the hundreds of others that are waiting for in progress dungeons. The length of time its going to take to get into a dungeon with a queued join in progress option is going to be staggering. Many people will find out its much faster to complete the whole dungeon then to sit and wait for in progress. I suppose adding the option will solve the problems people are complaining about here. It will just become a option no one uses. Or at least they'll use it once and if it takes longer then 5 mins they will just queue.