As you've pointed out, splashable black removal is rather limited at present. VoN will hit most of the relevant targets we want that aren't covered by Spear, but the color cost really wants 12 black sources. We got by with fewer in the early development of the deck playing VNH, but color screw can happen.Is sorcery-speed Dreadbore that good?
Ultimate Price is conditional, Victim of Night too mana intensive and Death Wind just stupid, but (correct me if I'm wrong) maybe Tragic Slip could find its place in here - especially if Lavinia atcually sees play.
Tragic Slip is likely too situational for this deck with only 4 cards as sac sources to actively generate morbid; it is best-suited in Aristocrats or a sac-
centerd Zombie build.
We're all sort of holding our breath to see if black gets a decent terror in DGM; if not, TS might indeed have to be considered.
As far as utility, Dreadbore is an excellent spell; there are very few things that Dos Rakis cares about that can't be dealt with at sorcery speed, and it takes out everything and planeswalkers to boot.