If that's "normal" I better take my truck back to Toyota!
Just had my rear pads and rotors replaced yesterday and everything is as quiet as the day I bought it. Oh, and lexus replaced my front rotors 30 days ago and no noise there either.
Did Lexus do the work or did you or another shop install aftermarket pads and rotors? This is more prone to happen with aftermarket pads/rotors. If Lexus did the work take it back and tell them to make it right.