So Soulrend Morgoneth reaper works really well. Its basically this build but with Morgo’s items instead and reallocating the points to max out SS and Nightfall. Alkamos’ rings makes the build smoother (total speed and pierce to cold) but Morgo’s rings are more flavorful (tentacle spam).
If I were to go the Vit caster route, I’d definitely use Nightbringer. Necro is the 1st mastery but what would be better to pair with it? Occultist or shaman? At a glance, occultist has more going for it with SoC, Pox and 50% converted DEE.