There is 3 parts to this:
    A sequence of actions that will make it so you log in the same place in the instance
    A sequence of actions that will make it so you don't get locked out of the instance after 5 retries
    A sequence of actions that will make it so either the eels don't respawn, or the chest does respawn (I don't know which, but the outcome is the same for the result I wanted)

So, to recap, the exact sequence of actions is:

    Walk into the instance (or get invited and walk in after, doesn't really matter since my rogue can take upto 5 save IDs) and stealth through to the eels/kill those
    Drop group to start 1 minute timer and log out
    Log in again, at this point it put me back at the front of instance, so I have to walk back to the chest area (I'm 99% sure at this point the chest has not respawned)
    Get invited,  drop group and log out
    Log in again, (from here out you keep on logging in at the location of the chest) loot the now magically refilled chest, take invite, drop group, log out
    Same thing, log in again, loot full chest chest, take invite, drop group, log out
    ad infinitum

I have been told a group of people are using flyhacks to instead fly underneath the dungeon floor to the chest directly and flyhack to vendor, works for herbs too. In doing so they don't have to log out and can whitewash gold through gbank, etc. Steamvaults is popular also.

The "legit"/nohack method is 4k gold per hour, no clue on the flyhack one
GMs were notified of this 9 days after the exploit went out after which they took another 2 days to act. 50-100 people knew about it to my knowledge