I use Sever, Blight, BCE and tendrils+minions on my Eternal Necro as shadow/minions.
Generators as shadow are a trap, between corpse consumption returning essence with passives and cold mages that give essence on hit with 5 mages (shadow mages are absolutely rubbish in comparison to cold mages+blizzard aspect for them) you shouldn’t need to slot a generator in your build.
Blight is honestly a rotating skill based on what I feel like using at the time, it’s main purpose is to apply 15% extra damage for myself and minions as tendrils pulls in before Sever spam to clear while everything sits in BCE puddles.
Bloodless Scream, Howl from Below and Mendeln are uniques while I wait for Sever boots.
Aspects are coldbringer, extra mages, minion damage reduction and both shadowblight related aspects.
Using extra skeleton aspect as placeholder for when I can get the Sever unique boots.
Use Cult leader, Scent of death, Wither and Flesh eater boards in that order.
Skip skeleton and mage specific nodes in cult leader, ignore +resistance nodes along the way as they don’t work properly anyway across the other boards.
You should be able to get everything good from the first 3 boards. Flesh Eater you will get the legendary node+glyph as well as 1–2 other node clusters depending on where you place your start point on that board.
With regards to 6 skills+minions at once. They are showing you which skills they recommend in your toolkit and what works for their opinion on the build I would assume.
Couldn’t tell you exactly as I don’t look at random websites telling me how to build.
Part of the fun is trial and error to see what works and what doesn’t as you progress, little bit of preemptive planning on paragon boards goes a long way as well.
The tricky part is getting the secondary bonus from some of the nodes in Wither and Flesh Eater boards.
The genius who decided to make both Int/Wis based classes have so many of their paragon nodes have a dexterity requirement should definitely go inhale some more paint fumes