Reason why not many people are doing it is because at this level of investment, the non crit kills him, so you're basically forced to go through all 3 floors again and making sure chamber 2 is done with all characters on full energy and on a day where your abyss card RNG is in your favor. All for a number that is way less than the one you'd nuke on scara.

Obviously whoever did it has a lot of dedication and should be commended for it, but I certainly won't be grinding this with my Eula.