I'm having exactly the same problem with my 2001 RX300. It started shortly after making a panic stop on the freeway. I routinely drive about 60 Fwy miles back and forth to work every day, and rarely have to do much braking. However, a person would think that a good set of brakes would be worth at least one panic stop without warping the rotors. I had them machined and the pads replaced immediately after the vibration started. It reduced the vibration to a mild pulsation. The mild pulsation increased to a strong vibration and I had the rotors turned again and the pads replaced again. Four months later the vibration is terrible...I can hardly hold the wheel. So today it's in the shop for new rotors and pads. Aftermarket.
To give the brake guys credit, they asked me all the right questions: overtorquing when the tires were rotated? driving on hills riding the brakes? cold water wash on hot brakes? I can't answer the tire rotation question. Who watches the tire guys while they rotate the tires! I could tell him, though, that I've made exactly one panic stop in 8 years, and NEVER ride my brakes. Perhaps they got wet while hot. But give me a break! What happens when we drive in the rain? Doesn't that qualify as cold water on hot brakes?
I'll be picking up the RX in about an hour and will post the results and the suggestions the brake guys give me.
