2006 Jeep Wrangler question

I have a 2006 Jeep Wrangler X and I have been experiencing steering wheel vibration for many months, the dealership has not been able to fix it and they have told me that vibration is normal for jeeps(this is not true b/c my mother bought a new jeep at the same time that I did and she doesn't have a problem). However, I recently had my tires rotated and balanced and this seems to have made the problem worse. When driving on the highway I can take my hands off of the steering wheel and see it shaking around quite a bit. And while the Jeep goes in the general direction that I point it, it feels like it's hard to steer and I have to constantly correct it. What should I have checked? It's gotten to the point that it is difficult to drive the car on the highway and keep it going in a straight line! I also often hear a slight clicking noise when accelerating, if that has anything to do with it.