That wobble is absolutely retarded. I have the same car and I hate it! Any small bump with any sort of steering input and the back end wags like a tail. It legitimately feels dangerous, and freaks out people when they are in the car. My motor blew at 60k (hyundai warrantied) and now at 115k my wheel bearings are shot (front it seems). I go through a set of brakes every season, it's a total rust magnet and it's not very good on gas. The second set of tires I put on wore very weird in the back, almost in a diagonal ribbed pattern. Mechanic said they had never seen anything like it before. And AFAIK there is no alignment adjustment on the rear of these cars: "Toe is pre-set at the factory, so it does not need to be adjusted. If the toe is not within the standard value, replace or repair the damaged parts and then inspect again."
I won't be buying another Hyundai, thats for sure!