From the FAQ:
Q:With regards to blessed weapons, which wound Undead and Possessed on a 2+. Do the list members here think that this would refer to all members of an Undead or Possessed Warband (excluding Hired Swords) or just Undead like Vampires, Zombies, Dire Wolves, and maybe Ghouls but not Necromancers and Dregs? And with Possessed, just Possessed models, not Beastmen, Mutants, or Magisters etc. (which would seem odd)?
A:Blessed water and weapons only effect Undead that are dead! Since Dregs and Necromancers are human, they are not affected. The manual actually states that Zombies and Dire Wolves are undead, and therefore can be wounded. However it doesn’t say in the book that Vampires are Undead but naturally they are. As for Possessed – Magister, The Possessed, Dark Souls and Mutants are all affected.
When determining who should be affected by blessed weapon in Carnival of Chaos warband, I see those similarities:
Carnival Master = Magister
Brute = Possessed
Tainted One = Mutant
And, of course, all Daemons (including the Plague Cart) should be affected too.