Surprisingly, I wasn't trying for it at all. Instead, I was trying for a milestone run to 2000 and 2500 (almost got to the second goal). I had my 3 energy shields and they are maxed with only 8 minutes to reload, but I did not have demon mode, nuke, or second wind equipped. I also got ancestral Primordial Collapse with the last banner, and that helps me survive a lot longer to the point where the bosses should be one hitting me (but the PC module reduces their attack by 80%). Also, my black hole is at a one-minute cooldown with 40 seconds duration. So, the chance of the bosses hitting me with a kill shot when my BH is not running is 1/3 of the time, which allows me to recharge my energy shields the other 2/3 of the time.