Activate Gloom and Desecrate
Gloom makes enemies slower and give you health on melee hit
Gloom makes you loose energy per second, Desecrate makes you loose health per corpse
Desecrate makes enemies drop more health and energy orbs
[Health Conversion] make you more tanky
This cycle of energy for health and health for energy makes Nekros into a farming machine on both, regular star chart and steel path.

Notes:
Range/Radius on [Despoil] is nearly the same as [Ignis Wraith] with [Sinister Reach] (Preffered weapon due to infinite punch through), 36.3m on Despoil and 39m on Ignis Wraith
Physique is better than Corrosive projection if you plan on running Gabii - Ceres, only for Steel Path Arcanes and Orokin cells, however think about adding an O/Aura polarity if you want to equip [Corrosive Projection] against Corpus or Grineer farming locations
If you really want to invest into the build, you can add an umbra forma to lower the drain of either Umbral Vitality or Umbral Intensify from 16 to 8 and add a D/Vazarin forma to the exilus slot and equip Prime [Sure Footed] for 100% knockdown immunity against Ancients, Scorpions, Heavy gunners, MOAs and Shield Lancers