As I read you have new rotors, it might not work, but nevertheless; On my old Jeep Grand Cherokee I had developing vibrations at certain pressures every couple of months.
The remedy I found was an early Sunday morning, an empty road, bringing it up to high speed, and brake the hell out of it a couple of times up till they started to fade.

 

This is a similar process I use when I do brakes on any of my vehicles...I call it seating the pads. I do as you, I run it up to 40-50 and get on the binders, but not getting into the ABS range. I do this 3 or 4 times and its always worked for me and no rotor issues.