This is the only [Nekros] build you need.

[Vigilante Pursuit] is a flex slot. You don't have to forma away the Madurai polarity but you don't need it. It's only holding you back, king.

All you do is turn on your Desecrate (3) and then go to town with a slash weapon.

[Equilibrium] is a bad mod and anyone that tells you any different got their build from a YouTube video dated back to 2017.
Why is it bad? You barely ever cast abilities and there are plenty of energy drops laying around. Between the health drops that spawn and the fact that you have a passive that restores your health every time an enemy dies near you, [Equilibrium] does next to nothing for you.

[Shield Of Shadows] is a quality of life nightmare and you shouldn't use it unless you're dying despite having +2550 armor and 90% damage reduction on top of it.

Your weapon needs to have at least 51% total damage be slash in order to trigger dismemberment.