Have you had any complaints regarding rear diffs and auxiliary fan belt tensioners on the 2011 VW Amarok? I have had our 2011 Highline looked at by the dealer after the belt started squealing and the rear diff began howling. Diagnosis is that the diff requires a rebuild, which VW are paying for the parts, but not labour. In regards to the tensioner the diagnosis is that the tensioner is moving around off-centre, and now the belt, tensioner and roller require replacing, but VW will not come to the party as they refer to them as consumables! Our Amarok has only done 61,000 km and I can't believe a vehicle with such low kilometres and been serviced by the same VW dealer can have these things go wrong at an early age.
The deal VW has offered you on the diff rebuild is the industry standard deal on a car that is a few years old and has done a few kays, such as yours. It's frustrating for you, but cars do wear out and do break down. Regarding the belt and tensioner, they are normally considered consumable parts and not covered by the warranty. If you could prove that it was design or production fault that caused the problem you could make a claim against the company.