This seems like an unfortunate side effect of the geometry of that cable mounting approach, doesn't it? When pulled taught (in the largest sprocket), the cable angle between where it exits the cable stop and where it enters that anchor is basically 0 degrees -- straight in. But when fully loose (in the smallest sprocket, and as pictured above), it's pulled that cable angle over to something like 60 degrees. That anchor doesn't pivot on its own, so it's just continually bending that cable. And these Shadow style derailers generally have pretty stiff springs as well, which probably just increases the force on the cable at that delicate point.
The fact that others don't seem to have problems with it suggests there may be other factors at play. But it sure doesn't look like a very forgiving design, does it?