Odd. I use the X8 on the Rohloff and it seems fine. The first one was changed at 4605km (I'm heavy on chains by the standards of everyone else here) and has been run in the conditions you describe, i.e. with no added lube, just the factory lube, and without turning over the sprocket which seems good as new. No noise with the original chain wheel (cheap steel crankset from India, not visibly worn at all) or the new chain wheel (Surly stainless) fitted recently.
The KMC X8 is fitted on Rohloff-equipped bikes by several upmarket European makers, though in the current economic climate some of them, trying not to raise prices, and therefore cutting back a bit on component quality, have started fitting the cheaper Z8. At retail, the price difference is marginal, and in fact some places the Z8, being in lesser demand, is priced higher than the X8. Go figure.
Andre Jute