Re: Holy Water
No, your argument is right. I'm not saying one shouldn't know how much damage it does. In a sense, the GM does need to know how much damage a small vial of Holy Water does to Frex, versus a Large Vial, versus a weapon dipped in Holy Water, versus an Oak Staff that was grown while only being watered with Holy Water.
HERO runs on numbers, and its good to know those numbers.
I'm just saying that, in a Heroic Campaign, the ability to make Holy Water should be a Skill, not a power.
I think that, whatever the damage is, the Vampire has a Susceptibility to "Holy Stuff," and as such, takes damage from Holy Water. But I don't think you need to build out the Holy Water into complete stats, because you run into other problems.
If you stat out Holy Water as working on Undead, and then the Priest throws it on a Demon, well, the Holy Water wasn't statted out to work on Demons, so no dice. Oh, wait, you want to dip a powerful evil sword in Holy Water to Dispel it? Well, it wasn't statted out that way. And you want to drink some Holy Water to cure the Necromantic plague ripping through your body? No dice, the Holy Water build doesn't have a Healing Power built in. And so forth and so on.
Instead, I'd just treat it as a substance, like water. There are rules for Drowning, because it is important for a GM to have those numbers. However, not every character with a Summon Water Power, or a Transform to Water Power, or a canteen full of water, needs to buy Drain STUN. I have a canteen full of water, and if I pour it into a doggie dish and shove an Everyman's face into it, he will drown, but I don't think I need to buy a Drain STUN, Linked to my Summon Water OIF: Canteen.
In MY book, it's important to know the numbers, but you can't stat out every implementation of those numbers.
In the Vampire Frex example, I think it's better to have the Vampire have a Vulnerability to Holy Stuff, and know what kinds of numbers are involved with that Holy Stuff, than to make stats for every kind and use of Holy Stuff.