seems unnecessarily random
He has to NOT use Perfect Dodge, Invincible OR Yaegesumi, out of a possible 5 SPs. So a 60% chance you will lose straight up. Then you have a 50% chance for aura proc method to be either Critical hits (the easiest to proc) or Simultaneous WS. The latter is harder to hit if people are spamming, but can be done if you see the first blue !! and everyone holds 2 seconds before firing off the WS. The problem is really just the players.
Folks seem hesitant to try it though. IIRC someone here said they used MNK for that purpose years ago.
This is how it was done early on for V15. Everyone off of Bumba the moment his window went up, MNK solo DPS would do multi-step SC (he'd get critical hits in between, so he would easily see if it was Crit aura), GEO would burst. If it wasn't either of those three, then it was Simultaneous SC just due to process of elimination. MNK would open and then rest would do SC timing WS and break aura, then finish him off. This would buy the group an extra 2.5 minutes if it was done on V20, but people saw you could "get lucky" by doing brute force method and figured it was easier to bash their heads into a wall dozens of times until it finally cracked instead of using another method.