-- There is almost no other situation where Scout is very useful. It's not even a good sifter, really.
Minion, Tactician, Scrying Pool, Vault, Wishing Well, against Ghost Ship and that is just from the top of my head...
Yes, Scout is bad. But still - he is an ugly cousin of Cartographer and Cartographer is pretty good so...
I really like Scout, it is my most favourite card from this list
Let me take these one by one:
Minion: When do you pick up Scout in a Minion game? Not in the first two turns, when you desperately need a trasher, or $$ to get to $5. Losing the Minion race is tantamount to losing the game in most Minion setups, right? I guess it's not a terrible buy if you have a random turn with $4 in hand... but getting all the Minions, and doing a little trashing, is way more important.
Tactician: It would be okay, except I can't see myself saying, "Yes, let me spend this turn buying a Scout with my $4 in order to hopefully pair it with my Tactician, hopefully draw at least 1 green card into my current hand, and minutely improve my Tactician hand." You would need like, a couple Scouts for that to be any sort of strategy, and I don't think anyone wants to defend buying 2-3 Scouts (unless Crossroads, GH, Nobles, and Harem all come to the party, and even then the Crossroads and GHs are more important for less money).
Scrying Pool: Since Scrying Pool decks tend to overload on Actions, I can see buying Scout (even multiple Scouts!) in this case. But Coppers are a bigger problem than Estates for the early Scrying Pool deck, and Scout doesn't do anything about that, so it's only a $4 I would buy if there weren't any other good spammable $4s--no Caravans, Mining Villages, etc. Scout might be helpful nearer to end if you have the right amount of money for it.
Vault: I don't think Scout meaningfully improves a Vault deck. Vault decks hit their target amounts of money pretty easily.
Wishing Well: Yeah, I agree with you here. Of course, since Wishing Well draws a card to begin with, if you're Scout does a really good job--draws 3 green cards into hand--it won't work. So interestingly, Scout failing to do what it's supposed to do is one of its better uses, when paired with Wishing Well.
Ghost Ship: Yes, but similarly to Rabble, I don't know if it's a meaningfully good counter unless you have a bunch of Scouts, and you'd still rather have Farming Village or Lighthouse.
So, you're definitely right that I misspoke earlier. Scout can be useful in a few other situations. But I'm not sure it's more useful than buying a different $4, or just buying Silver, most of the time, even in those situations.