This is a very situational weakness. While you are never happy to see your demonic "friend" show up, sometimes it absolutely wrecks you, while other times you can limp to the end of the scenario without too many regrets. In some ways, it the exact opposite of Searching for Izzie or Cover Up, in that, if you have to draw it, the last turn or two is when you want to do do so. As usual with the to remove weaknesses, this has much greater impact in solo than multiplayer.
While this weakness is probably less annoying overall than Occult Scraps, the "box" signature weakness, neither is too terrible, making Dexter one of the investigators who should think seriously about including both sets of signature cards in one deck.