Great goobers that card is ridiculously powerful if you can draw AND underdeck your opponent's cards in play. Who designed it?
It was designed with the intent of combating the powerful Throne and BoM decks that use multiple brigades as well as the new Martyr theme that typically uses several brigades. It was also designed to give players a way to "catch up" if the opponent gets out to a huge lead in cards in play. In a T2 game at Iowa State last week, my opponent and I took turns triggering our Outsiders (he used his to underdeck several of my cards, but that gave him the card advantage so I was able to do the same thing to him during his next attack).
As mentioned by Jeremy, if a player is using a mono-brigade offense like Angels or Disciples, they won't have to worry quite so much about Outsiders.