they really ought to add a glyph that switches the special ability you gain from whichever demon you sacrifice to that demon's other special ability: make it a minor glyph and we could use it for niche encounters.
Voidwalker: Disarm instead of Shadow Bulwark
Felguard: Axe toss instead of Pursuit
Felhunter: Devour magic instead of Spell Lock
Imp: Cauterize instead of Singe magic
Succubus: Whiplash instead of Seduction