If you've had a wheel dropped for any reason (tire balance, rotation, etc.) and they did not torque wheel nuts with torque wrench their is a high degree of rotor warpage likely.
That slight vibration could also be from warped rotor that you seem to confirm with the presence during braking.
But it could also be from flat spot on tire, a difficult to balance tire that would fare better with a RFB (road force balance) done with a special machine.
The rotors seem most likely, but it is possible because the pads also come in contact during braking that you are transferring more of the offense from the wheel assembly through the suspension.
