Yara's Violent Unraveling: "The XXX is unaffected".

[monkeytor]

I've been playing around with YAR and on a couple occasions when as far as I know the spell should work with the given effect (A couple specifics I remember are a hasted deep elf and an injury-bonding death knight), I get the message, "The XXX is unaffected". What does this mean? Can the spell be resisted? If so, there ought to be a % success chance listed as with all other Hexes. Or is it something else?