This is one of those cards that is deceptively good. I thought it was just ok up until recently, but then discovered just how great it can be - especially in multiplayer games.
This is really easy to thwart down with high-attack heroes; and you can leave it sitting out as a panic button for if the main scheme gets out of hand. Being able to suddenly clear 15 threat off the main scheme - as I did in a couple of three-player games - is just incredibly helpful. IMHO, a card that has a much better design than is first apparent.