This is pretty simple.

SE would have to implement some way to lock an area down until all CS are over. Until then most groups are going to run them fast. I don't even queue anymore, but when I did 3/4 parties didn't even contain a new player. The ones that did usually there was only one person. This becomes a needs of the many vs. the few situation. The only reason those people even get a queue in the DF is because people are running it for tomes and exp. Last of all, if you wanna do a dungeon and keep it storybased, make a PF. More often than not people will run it out of pity for someone and let them watch the CS. Ive done it, and not its even easier if you can run it uncapped. You can clear it with 2-3 people I would assume.