It doesn't seem intuitive for an attack to fail because you revealed a Moat or had a lighthouse in play last turn, or for the 2nd part of the attack to succeed despite you revealing a Moat.
Duration attacks are fine (although many disagree), but the attack should only take effect immediately upon playing to avoid those confusing rules parts.
If you do want an effect across turns, you could do a non-attack interaction, like Bishop (make the trashing optional), or an attack that hurts opponents both this turn and next turn (like Ghost Ship).
As for the card itself it seems fine but doesn't seem to offer much above and beyond Chapel as far as game experiences go. Being able to trash every bad card in your deck with a single play may make 5/2 openings too good. However what it does offer uniquely is the very high risk, like Lookout, and while this isn't necessarily a bad thing, I personally can't stand the high risk gambling of Lookout as the game progresses. You've already invested in buying the card, so it doing nothing for you is bad enough, but actively hurting you is awful. In IRL games who'd want to be the person who tells the other players that they do in fact have to trash at least 2 of the cards in their hand when they don't want to trash any?
Then again every player is different and that's just a personal opinion. If you like that kind of card then who am I to judge.