I think they overestimated just how much of nerf Netherlight Crucible would be. Yeah, sure, the dps boost makes certain things easier and you might kill Avatar from 35% P2,
but a single failed soak (meteors, touch, armageddon, Maiden's orbs) is still an instant wipe
. Doesn't matter if you have 60 traits or 75, higher output doesn't change a thing. Extra traits were much bigger nerf to Nighthold than the Crucible, but this goes back to boss design being less obnoxious.
It would also explain why they waited so long for actually meaningful nerfs - and still didn't quite deliver them with KJ. "Just wait for that next tier of traits, the kill rates will surely skyrocket."