I'm just going to come out and say it: I like Scout. It combos with a lot of things, and I personally do not think it's horrible.
1. It combos with Crossroads for a deck that can use Victory cards as draw.
2. It has a weak combo with Wishing Well.
3. Can defend against deck inspector attacks if they leave Victory Cards on top of your deck.
4. Can let you draw more cards with draw-to-x, and can control what those cards are.
5. Harem, Nobles, Great Hall, etc.
6. Can combo with discard cards like Oasis and Inn (you draw Victory cards then discard them).
7. Mystic, Mystic, Mystic!
That's my opinion, but I think a lot of these reasons make Scout a card that you could buy every once and a while, and benefit from it!
1. Crossroads+Victory cards is almost never a viable engine option. Scout doesn't change that.
2. So you play a scout, then a wishing well. Okay, most likely you end up neutral, besides knowing what the top 2 cards in your deck are. Occasionally, you will have a 2-card lab, but that is really weak for a 2-card combo, especially one that has a card that is more-or-less dead outside of the combo. And then there is the opportunity cost... which is far too high for something as bland as that.
3. That is still very weak, and scout could well miss the attack.
4. This reason is very confusing. You play a card that does nothing so that you can draw one more card? That doesn't actually help draw-to-x cards at all; if you hadn't had scout, you would have drawn that extra card anyways. Sure, it lets you reorder the things on top of your deck, but again, that marginal benefit is far too high given its opportunity cost and what happens in the event that you do not manage to couple scout with your library.
5. You need 1/4 of your deck to be these cards before scout is not a drag on your deck, which takes a lot of effort, and can stymy your engine building in other ways; you may feel the pressure not to buy other things like villages and such. The only thing listed there which could make scout even close to not being a drag on your deck is harem+scout, but that is going to be hard to set up, and by that point you probably have terminals in your deck and may not want to risk drawing scout, for example, with a smithy. And again, let us not forget; scout carries with it an opportunity cost, and merely not hurting your deck doesn't make it a worthwhile buy.
6. This is just not viable 95%+ of the time. Having upwards of 1/4 of your deck be victory cards hurts your engine too much for something like this to be viable.
7. You need to collide scout with at least 2 mystics for it not to just be an overpriced, 2-card silver. Even then, it is still just a 3-card grand market + silver, which is extremely weak, given that it can miss and has a lower effect than buying 2 cards that are actually at the same price as the mystics that you bought. In addition, the chance of colliding that much is far too low to be viable.
All in all, i would not hesitate to call scout the worst card in the game. Some people like to give the title to thief, but at least with thief there are some non-contrived situations in which it could be useful (if your opponent goes for gardens, for example).