As I point out on Joe's site, the range of conceivable V-class objects is infinite; thus, it's impossible to calculate their probability, or improbability.
At first glance this seems so obvious as to be unworthy of notice. Since we humans do, in fact, continue to exist, it shouldn't be surprising that vampires (and other V-class objects) do not exist. But this begs the question of why humans exist and V-class objects do not. Their existence is, after all, as probable (or improbable) as the existence of humans. And the non-existence of any V-class objects is as statistically improbable as the aligning of dozens of independent physical constants that give rise to life.
The anthropic principle could therefore be restated as claiming that the existence of human life requires both (a) the alignment of several cosmological, chemical, and physical constants and (b) the non-existence of all V-class objects. The probability that each of these stochastically independent events could align precisely as they have, without any intervention, is roughly 0 -- in other words, it can't happen. The evidence therefore points to "fine-tuning" of these conditions.
Whenever you have the urge to invoke vampire math, resist it. Please.