The Haldex failure could be attributed to lack of fluid and filter changes. When the original Haldex was fitted into the Audi quattro, the fluid and filter changes were at 12K miles. This added at least £100 to the annual service price. For this reason, I believe that once a Haldex quipped vehicle reaches an age where the owner considers dealer servicing is no longer cost effective, the important fluid/ filter changes are missed. This would cause failure of the pump and hence the unit itself.
The diff failure is attributed to the bearings being to small for the job in hand, giving a life of 50K miles or so.