Maybe "reveal cards from the top of your deck until you reveal two different cards, then trash the lower value of the two?" Because otherwise if you reveal two provinces, trash one.
It reduces the swingyness, though still makes it really swingy.
And for the reaction portion, its a wording reword, "If you do, the player may trash the attack or the effects of the attack are reversed and the attack card is returned to the player's hand. Either way, this is highly un-dominion like. I'd make it cost 5 at a minimum to help with that, but it's more swingy than Saboteur, and most people who play dominion (myself included) won't like that as it radically changes the game.