The Bite-Sized series of articles is meant to take the most powerful cards in Dominion and give a short explanation of what makes them powerful.
Scrying Pool is one of the few sources of unbounded draw in Dominion. In an action-dense deck, Scrying Pool can draw you an obscene number of cards without even using an action. This, coupled with the attack, makes a strategy based on drawing your deck with Scrying Pool much more powerful than it might seem on a lot of boards. Trashing your starting cards is one of the best ways to get an action-dense deck, so it can be worth delaying your Potion buy until after the opening to get started faster.
Even in decks that aren’t action-dense, Scrying Pool is still worth going for, as it can still draw a significant number of cards, especially when you consider that the sifting effect for your own deck is often as good as drawing an extra card. It’s usually only skippable in heavily treasure-focused decks with limited gains, because in these games it takes longer to get an action-dense deck up and running and it’s more difficult to overcome a points deficit.