A little digging into the Santa Muerte phenomenon has convinced me that it's a sick joke created by organized Satanism, although it apparently has the significance of a rabbit's foot to most of its adherents.
From the perspective of the Mysteries, Satan is the god of death. "Ritual" murder (Frantz Fanon's "holy violence") is an important aspect of Satanism, as Rudy Guede can attest. Its purpose is to elicit demonic possession, although it has to be performed with a certain attitude, and is sometimes associated with sexual pleasure in an attempt to align human will with demonic will. So, not surprisingly, "Holy Death" is an alternative term for Santa Muerte, i.e. Saint Death. ("Santa Muerte" also just so happens to convert to 137, i.e. 11, the number of black magic, which Satanism pretends to be, to some people.) Skull & Bones venerates death as a supposed great equalizer, which exposes their belief system as existentialism and wishful thinking.
Dressing up a symbol of death in saint's garb also happens to be an apt symbol for what Satan hopes to do by means of the fake apocalypse, which is to con us into accepting him as Christ.