My front rotors were experiencing some warp within 5-10k miles after turning them (turned them twice after warping). I thought maybe there was some defect in them, so I just replaced them (rears too) along with new pads.

I've also been watching my front and rear suspension for bushings and ball joints wearing out. So today within 100 miles after the break work, I noticed a little bit of vibration and shaking in the steering wheel when lightly breaking. It makes me wonder whether there is some wear in the suspension causing the vibration and maybe leading to the rotor warp.

Any thoughts on this or what might be causing what seemed liked premature warping of the rotors?

By the way, regarding suspension parts, I just noticed at RockAuto what appears to be a ball joint for the front upper control arm. I was under the impression that these were absolutely not available separate from the control arm. What do you think? Is it a ball joint for something else?
2004 JAGUAR VANDEN PLAS Ball Joint

 

No those ball joints aren't for the upper arms, but they look very much like the elusive lower ball joint from the Brembo equipped XJR, SuperV8 & S-Type R.

 

Looks lie the ball-joint on the hub carrier to connect to the lower wishbone. These are very difficult to swap out due to the shape of the upright.

However there is a part number, so check it out.

 

Suspension/brakes guy took a look today and said I got a bad front new rotor. Claimed they warp just from getting knocked over or stacked on end. That's what's giving me the little shake in the steering wheel. So I'm returning it and getting another one. See if that does the trick.

He also said all my suspension parts look fine, bushings, ball joints, and all. So that's nice.