The power of this build is from Gloom with Hunter Adrenaline.
There is a free mod slot open for Primed Flow, [Intensify], Auger Reach, or [Preparation].

I've messed around using Umbral mods but they don't add or subtract any value compared to this build but use a couple Forma.
Running [Overextended] to increase Gloom reduces strength that you later make up with Umbral Intensify and end up with 95% strength and only 5m more for Gloom.
You do have less health from not having Umbral Vitality with Umbral Intensify but most of the time you won't need that extra health as you won't be getting low if you're using Peacemaker. Plus Wisp exists.

Primed Flow gives you around 60 seconds of staying in Peacemaker without taking damage. You could take it if you feel like you're constantly running out of energy from killing things too fast.
[Intensify] can give you a 30% damage boost during Peacemaker.
Auger Reach can give you the range that you're missing from [Overextended]. If you notice the extra 5m being a make it or break it, you might want to take this.
[Preparation] lets you start the game with max energy, but since you don't have Primed Flow it won't make as big of an impact, so only take if you need to start with energy which in most cases is never.
Optionally use whatever mod you feel fits best.

How to:
Get enough energy to flick on Gloom then you can leave it on for most of the mission.
Take health damage to get your energy back.
Get a headshot to trigger Arcane Precision.
Blast everyone away with Peacemaker also getting your health back from Gloom.