But... if there's a better way to draw than Werewolf, you don't care if you lose the Werewolf split.
More generally: if Werewolf is the best draw on the board, you probably want to be buying Werewolf and also probably want to be making sure you can play those Werewolves for draw. If Werewolf isn't the best draw on the board, buy the thing that's better instead.
What you're saying is unrelated to the point I was trying to make. You do understand this, right?
I'm happy to discuss the things you're saying. Let me first generalize them, probably too much:
If there's a better way than card X to do Y, you don't care if you lose the X split.
More generally: if card X is the best way to do Y on the board, you probably want to be buying X and also probably want to be making sure you can play those Xs for Y. If X isn't the best Y on the board, buy the thing that's better instead.
If Minion isn't the best virtual money, you don't care if you lose the Minion split. If Bridge isn't the best source of +buy, you don't care if you lose the Bridge split. If Mint isn't the best treasure gainer, buy Bandit instead. If Count is the best virtual money, you want to be buying Count and playing it for money. If Minion isn't the best virtual money, buy Mandarin instead. If there's a better way to gain Estates than Wild Hunt, you don't care if you lose the Wild Hunt split.
If Jack of all Trades is neither the best topdeck inspection, the best Silver gainer, the best draw nor the best non-treasure trasher, you should buy what's better at each of those things. So on a 5-card board with Moat, Hermit, Cartographer, Explorer and Jack, I shouldn't buy Jack, I should buy the other cards instead.
If you're evaluating a multi-faceted card in terms of only one of its facets, you're very likely to be evaluating less accurately than if you consider all its facets. In particular, there's value to the modality of modal cards, even if they're not best at any one thing they do.
For example, on a board with Village, Smithy, Bazaar, Patrol, Woodcutter, Festival, Band of Misfits and Donate, the BoM is not best at anything it can do, but it's not obvious that it's always optimal to get zero BoMs. In fact, I would be surprised if it was.
Maybe my examples are bad because Y=draw is special. If so, why—why is your mode of analysis appropriate when comparing cards that draw but not other cards? And if draw is special, I should definitely buy Moat over—or at least in addition to—Jack, and play it for draw, because it's better at drawing, right? Or are there other specific characteristics of Werewolf that are relevant to your general point?
The way I read your comment, and maybe I misread it, is that Werewolf should only be evaluated in terms of its ability to draw cards. I think that's a bad approach, as I have just argued.
I have observed that there's disagreement about the strength of hexing your opponent. If you belong to the camp that says "hexes are so ultra-weak that you can ignore them", an analysis of Werewolf that's limited to its ability to draw cards is fine. But that's because you evaluated the other facet of the card!