So I did the dunegon Cragmire Crypts, and I kept getting DC'd in the dunegon. Now the thing is, everytime I got DC I coul re-loot all of the chests inside the instance.
I would assume this would work for every instance in the game!
1. Enter a instance
2. Clear until a chest appears
3. Loot it,
4. DC
5. Loot it again
Repeat from step 4.
Enjoy!
EDIT: You can acctually leave the instance and re-enter to reset the chests!