Feels like they wanna put more of the weight on the Challenge Log to stop people from grinding the fuck outta NM's and force them to play longer. Stay classy, SE.
Also: According to this doc, that boss gives like 80k at lvl 22. So looks like it was being underlevel that did it.
It'll prolly end up being a similar grind, as people figure out the spawns and you start clawing your way up past loloneshotbait, same as Anemos. I don't know why anyone finds that fun.