Hi sorry to read about your rx problems.I have just bought a 55 rx400h,when i tried the car it pulled badly to the left the dealer lexus hedge end said it was down to the tyres.when i collected the car they said it was all sorted and had cost them £200.I took delivery and it did feel better but still not right so took it to a tyre dealer who has looked after my previous cars and always gives good advice.when they checked the rx in their words "it was a mess" all the tracking and geometry was out and the car was "crabbing"after they corrected it the rx felt great.try and find a tyre dealer who uses computerised tracking geometry and the staff to use it.
Regards and good luck.Kevin.