This is a bug related to the recently patched BST pet issue Cory was having:
Invoke Death is supposed to summon a lvl 46 Spectre Pet base.
With Minion of Darkness focus it summons a lvl 41 Skeleton Pet.
Please make Minion of Darkness add levels instead of subtract (from 46 up to 51 instead of 46 down to 41).
I was going to make a long post about its lack of survivability and being unable to proc on current content but I believe this would take care of it.
Thank you Eld.