[Chaos]

Holy's ~existence~ is kind of silly to begin with. The fact that it approaches nearly 200% of normal damage in the hands of a priest with the traits invested is a slap in the face.

Holy only works for basic attacks, and only when it's applied against its target audience. In fact, it's a prime reason why public Vampires are not a good idea: not only does the lore state that most vampires stay out of the spotlight, but the Church has several tools to use against them. As a Vampire, your best defense against Holy is not letting anyone know that you're a Vampire. Once you go flaunting your race, you've opened the door for others to justifiably wield Holy weapons against you.

On the other hand, I think Holy should not be something that you can slap onto a weapon and call it a day over. If just 'more damage vs. these guys and nothing against others' is making Holy an easy choice, then I'd suggest balancing Holy with a -25~-50% damage modifier against any race that wouldn't trigger the 50~75% damage boost.

In either case, you really shouldn't be gaining the benefits of Brighter Darkness when you're not only a Vampire, but also Possessed. If you want to argue logic about this, then consider that a 'Possessed Vampire' trips not one, but two conditions of a Holy weapon.

P.S. Holy gives +50% damage at base.