I had no problem with Deadmines. I had 2 toons at lvl 21 and wanted to start 4-boxing, and deadmines was great!
I parked my 2 low lvl toons at the begining of the instance (just when they got inside = no /follow !); Used my 80-mage to go over every "living" thing (just run, don't kill) including the 1st Boss ; ran back to the start of the instance; kill everyone with AoEs. Repeated that for all Bosses -> no pats, no aggro for the little ones.
After 2 hours I got tired and started to 1 shot the first bosses to open the doors and drag almost all the instance to the beginning.
Now I'm running instances with my team w/o the 80s help, It takes longer, but is more fun IMHO