Hello, I found out this exploit by pure luck. When you choose "turning the tide (2nd quest in act 3) - begin quest", you may interfere with those green hounds, Fallen Monrel as elites. If you get chased by them and run down the stairs in the start of the area they will not run down the whole stairs and stop in the middle meanwhile you can kill them below the stairs in peace.
While it takes like 1min to clear normal mobs you can just leave and resume game until mongrel elites spawn and so on.
I did not have any elites with me but this works as intended with normal ones aswell so i took a pic.
While I did this on my monk, I just use deadly reach attack to kill them from where i stand in the picture.
https://i.imgur.com/XavEN.jpg