Hmm, well, I've had a 4 Rabbits/Jettas of the "1st gen" type, and my Dad has had 5. Plus, I had a '96 Passat TDI, and now own a '04 Passat TDI. With two exceptions, all of them have gotten over 300k without ANY engine problems and NONE of them have EVER been sold/retired because the engine was worn out. The first exception was my Dad's original '78 Rabbit, the car that started us on our long VW diesel sojourn - it self-destructed the head at 287k, but that was because the timing belt broke, and it had NEVER been changed, so it was his own fault. After that, all of them got timing belts replaced every 100k or so. (He rebuilt the head, and put another 100k on it before deciding to make it a parter because of wear and tear on the rest of the car. ) The second exception is my '04, and I guess everybody can figure out why it hasn't made 300k yet - it's only got 12k on it so far.
Now, that having been said, every one of those VW's, except the original '78 my Dad owned, has run Amsoil in it, with yearly changes. Other than that, I can't tell you why our experience seems to have been incredibly atypical...