Normal ? No, definitely not.
Common on IS200 ? Sadly yes it would appear so.
Fronts seem to exhibit wear associated with excessive 'toe-out' alignment.
Speaking to a colleague, I gather Mondeo's are prone to this too.
In the Fords case, it's due to some bushes which wear out quickly.
Coincidentally, i asked Lexus about this earlier today - await reply.
Just had new tyres fitted. Old fronts 4mm or so except inside edge which is bald.
Regular alignment checks (by lexus) - most recently Feb at TTE - always ok.
I've suggested the following possibilities to Lexus ...
1) Static alignment ok but changes once moving - something worn / broken ?
2) Alignment specs in manuals / alignment gear are in error ?
3) Specs chosen by tyre manufacturers - Lexus possibly on commission
See if they have a solution - hope so given that lots of people have the same problem.