I'm fairly impressed. Every time I think 4e will wuss out on something really tough, something save-or-diey, they always surprise me by being pretty harsh. The rust monster still destroys magic weapons and armor... it then supplies the party with the weapon's exact value after they kill it, sure, but I was still surprised that the designers were still willing to leave a PC weaponless for an encounter.
And now this. I was thinking they were going to make the minuses really weak, but some of those mess you up. Euryale seems harsh, and then there are of course those two that imprison your mind or body.
I do agree that they shouldn't have made it such a good implement. Personally, I wouldn't of made it an implement at all. I'm frankly wondering what incentive a PC would have for drawing from the deck at all. The only thing I can think of is borderline DM fiat: "The deck tempts you to draw from it with its chaotic allure. Does 29 hit your will?"