I have killed tons of vampires, explored vampire caves, completed the Volkihar questline(including the minor quests) and what not and still no Vampire Hood to be found anywhere.
I have visited shops and it's not being sold either.
I then decided to make a DG Vampire Hunter to see if it'd drop for him and it turns out that I get a quest which involves killing a vampire who wears the Vampire Hood. I later found it on a vampire again....
What on earth was Bethesda thinking when they made this dlc? Vampires shouldn't be able to obtain their own armour? Really?
I honestly don't even know what to think of this... Vampire Hunters have acess to Vampire armour but Vampires don't? What were they thinking.....
In case you don't know what the Vampire Hood is: http://elderscrolls.wikia.com/wiki/Vampire_Hood