As it was imba, so it remained.

For Arbitration i recommend Arcane Blade Charger and Arcane Primary Charger

For better strong, you can replace Armored Agility/[Adaptation] with Augur Secrets (not recommend).

For mobility (speed and fast armor), you can replace Adaptation with Armored Agility.

Guide - https://overframe.gg/build/22009/nezha/sentients-killer-endgame-universal-build-umbra-charged/