Suggestion: The soulblight gravelords should be splitted in more sub-factions with their unique trait.
Stay with me for a second, we have so many cool "Themes" Skeletons, Zombies, Vampires.
And the trait helps only the vampires.
If you want to make some thematic warbands they basically have all the same abilities.
I don't mean something like another faction.
I mean something like the flesh eaters and the royal beastflayers.
Or the kruelboyz and the kruelboyz monsta-killaz.
Like, "Kings of the death" and you put inside the son of velmorn and the Skeletons.
Or Children of the night and put inside every vampire.
The minions have their unique faction, like gobbapalooza, and when added they act like ally. If you add minions and have no vampires you want Deathless minion as a trait anyway.
Basically you choose your necromancer faction and then add minions.
Sorry guy a little rant because the soulblight has so many cool models but you end up basically play always the same faction.