The vibrations are internal, and can't be seen on the outside because the bearings are holding the whole system. I agree that any diff is really meant for short term use, but if it can be built with excellent symmetry, then it should last longer than a few runs...Ball diffs don't have symmetrical issues, and I think they can be made to work better: stronger diff bolts, better locking mechanism, titanium or steel ring&pinion gears, etc...