Minions..!

After my necromancer raises about 10-15ish bone horrors, some of them start dying even when i cast verata's sacrifice! is it just me or do their HP seem to degenerate faster when theres more of them?

You know how, when you're out of combat, your HP goes up slowly, then a bit quicker, then even quicker? I think that summons start out with -1 health regen, then get -2, then -3, etc. Eventually you won't be able to save them with just Verata's Sacrifice.

I think your right, best bet get a monk to spam heal area for your little army

I don't think it's worth energy trying to save them after they've past verata's sacrifice's benefits... let them die, with the energy you saved you could create fresh ones. Of course this doesn't work when there's no corpses around, but i still feel it's better to just let them die and use your energy more wisely, since in combat they're gona die in a second with that hp degen.

Start a fight, any natural regen you have ends and in the same way any natural degen minions have also ends.
Dont heal them, they are meant to die for the soulreaping

If you run n/mo you can keep them alive for quite a while with vert sac and heal area outside of battle, make sure you use it constantly every time it recharges. The minions automatically cluster around you so heal area is easy to use in that regard.