Mike, at last someone has the same problem as me!!
My is300 has had 6 NSF discs, have fitted new brake pads (3 times) rebuilt caliper and carrier, wheel bearing replaced, flexi brake hose replaced with no joy. I was thinking along the same lines myself but will take a chance on a "used" hub.
I really cannot find anything else that could cause the disc to warp, mechanics have had the car up on ramps and have checked all ball joints etc etc, but have no idea of the cause. Previous owner may have whacked a kerb or even another car hitting the wheel/hub, who knows...but I reckon that changing the hub assembly is the next step.