Why are the brake discs wearing so fast on our Mercedes-Benz A-Class?

My wife's 2008 Mercedes-Benz A-Class brakes have started to 'judder' and, after its latest major service by the main dealers, the discs were found to be 'warped and corroded' but with still plenty of pad life left (8-9mm). I didn't receive a satisfactory explanation as to why this should occur after such a low mileage (21,000 miles), although corrosion was mentioned due to having had little use. Having driven Mercs for many years I have never had this problem, even after 100,000 miles, so I wonder if there is a manufacturing fault with this model and if it is worth pursuing with Mercedes, as the cost for new discs and pads is around £670.
Since asbestos was banned from brake pads, pads have had metallic content and discs have had to be made softer to give the same braking effect. A consequence is that discs rust and, if a car is not used regularly (which takes the rust off the surface), corrosion eats into the discs.
Answered by Honest John on

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