Okay, here's what this trick does...
From what I can guess, its a way to trick the game into thinking someone has left your group and then "finding replacements". As most of you already know, when the game replaces someone, your group is put in the front of the dungeon line. Using this method, you and 1 other person are able to chain queue whichever instance you want with ~30 second queues(regardless of class).
1. You and a friend group up and queue for a random dungeon... This is the only initial time investment required for this.
2. Complete this dungeon. The purpose of this is to put your character into the dungeon system.
3. When the dungeon is over, do not leave that group. Let all the other randoms leave.
4. Now either you or your friend needs to physically go to a dungeon that is different than the one you just were in. i.e. if you did Halls of Origination as your random, then physically fly your character to Grim batol and run into the instance.
5. Now once your loading screen goes away, open your queue pane and it should say: a player has left your Grim batol would you like to find a replacement? Click yes.
6. Enjoy your 30 second wait while you are put at the front of the line... Then after this instance is complete, redo the previous steps for another 30 second queue.
Using this you can spam queue dungeons. I'm assuming this would work on heroic as well as long as you and your friend aren't already saved. Overall, this needs testing but it could be very useful to some DPS who want faster queues.
Its great if your battlegroup is like mine and dps queues are 30+ minutes lol... Also, I'm sorry if this is common knowledge or has already been posted.