So my buddy was leveling a wizard and we were testing the act 3 method where the explosion kills the mobs.. too slow
So we went to act4 nightmare and we killed iskatu fast. I asked him to try and solo it by running to the corner, casting hydra and archon and just hold right click. He was able to solo in mediocre gear.
So if you have the gear im sure u can do this on normal to nightmare to hell and get 60 fast.
The run seriously takes less than 1 minute if you skip the dialogue.. enjoy while it lasts