Well... the Nexus 8-speed hub I switched to was making its own unhappy noise. Less loud and less gritty than the alfine, but clearly not healthy, or so I thought. The nexus hub had about 9,000 miles on it with annual oil dip and greased bearings. Like the 11-speed, it was shifting perfectly... just making worrisome noises under load.
Luckily, I have yet another Nexus 8-speed hub, which has been used on my "winter" bike. Its total mileage is less than the other. I installed it today and took it for a shakedown ride; it is smooth and silent.
Now that I have reliable transport, I can look into the problems with the other hubs.