Volkswagen Amarok 2013: Excessive front brake wear

I recently had my VW Amarok in for a 45,000km service. When I inspected my front brakes before the service I noticed that my disc rotors seemed noticeably worn but my brake pads had around 50 per cent wear. After the service the report stated that my disc rotors were only just legally over the maximum wear tolerance. I discussed the issue with VW and explained if the vehicle had travelled over 45,000km and the brake pads were only half worn I am obviously not a heavy braker and there must be a fault with the disc rotors. I was told that as far as VW were concerned this is not a valid warranty issue and brake pads or rotors are not permitted as warranty issues. Disappointed in this response I rang VW customer care and was told that VW did not approve warranty on brake issues. Does VW expect Amarok drivers to replace two sets of disc rotors with each set of brake pads? I feel this is extremely unsafe that a disc rotor is worn out at twice the rate of a disc pad.