Very solid [Nekros] build based on his 3rd ability: Desecrate.

Mods:
[Vitality] and [Primed Vigor] for a lot of health, it works great with arcane grace.
[Overextended] and [Stretch] for range.
[Health Conversion] for +1350 armor.
[Adaptation] for that 90% resistance to elements.
[Fleeting Expertise] for Desecrate, it will use only 3 health per corpse.
[Despoil] for Desecrate,

Arcane:
Grace very good arcane for health [Regen].
Strike not mandatory you can put whatever arcane you want.

Suggested melee: Slashy boi
but you can also use other slash based melee such as: [Gram Prime], [Galatine Prime], [Orthos Prime], Zaws, [Kronen Prime] and so on

Companion: Helios with his Deconstructor