To confirm your claim about "bad right out of the box"...I will relate a story about a brand new 1989 Ford SHO that I purchased...

Both rear rotors were so bad that the wheel hub bearings squealed every time I stepped on the brakes..including the ride home from the dealer the day I bought the car. I finally dial indicated them myself, because they were giving me such a hard time about replacing them..."pads and rotors not covered by warranty"

To do this I trued the outer rotor on a lathe to .000", and measured the runout on the outside edge of the mounting face...much smaller than the rotor in diameter...I got 0.170" runout. You can imagine what the runout was if I trued the minor diameter and measured it on the disc face...maybe double this figure....The callipers and brake pads would prevent the disc from wobbling too much, but the force caused by this deviation was actually flexing the axle shaft, and stressing the tapered roller axle/wheel bearing..causing the squeal.

With new rotors the sound went a way...but at 70,000 miles the right rear axle shaft snapped..while I was doing 75 mph on an interstate highway. An inspection of the sheared axle assembly showed heat blueing all around the failure point, which would have been where the center of the flexing took place.

The left rear had the same issue but not so bad..0.070" runout measured the same way (at the outside of the mounting face..ie minor diameter) The left rear had not failed before I finally sold the car. Never assume that because it's "OEM" that it's right...however the odds are still better that it will be more frequently than aftermarket stuff.