Funky Rear Suspension?

I've had my 2002 Allroad for ~ six months and love it, but I've got a question for my fellow Allroaders.

When traveling at virtually any speed, if I go over a moderately rough manhole cover or pothole, my Allroad steps to the side when the rear wheels travel over the bump. The right rear seems to step to the side more so than the left rear.

I took the car to the dealer today and they inspected the car and said there could be a couple different causes. Are you ready for this?

1) The tires are worn and slightly cupped on all four, according to the dealer.
2) The rear rotors are slightly warped, according to the dealer.

Now, I know a little about cars, including suspension and brakes and I'm having a hard time accepting their reasoning. The inspection found nothing, but a CV boot that has a crack in it, again according to the dealer.

I don't have a problem purchasing a new set of tires and/or replacing the rotors if warped or worn, but I can't believe this is going to correct my problem.

I'm ready and waiting for your expertise. I've posted this in a couple forums, so you may be re-reading this.

Thanks!!!