The walkthrough of the mines is as follow :
Destroy Totem -> Talk to Miners -> Slip through the Death knight to the big door at the extreme South-East -> Talk to the door and give it the password learned from the Miners
Make sure to do every side quest / fight before going through the door.
The Mines seems to automaticaly Cave-in at the end, so you won't be able to kill/talk to anyone in there.