Absolutely. I've done it. Massive vibrations, had to vary the speed constantly basically undrivable, rear view mirror shaking so bad you couldnt' see out of it. Regrease, good to go.
I think Marshall from MWE used to get some new parts, unless I'm just mis-remembering. I heard him say something over the phone to me one time about new parts 20 years ago, so there's a lot that could go wrong in that recalling? I haven't heard of people really rebuilding with new so I assume they don't exist now or it isn't cost effective.
Axles can wear without breaking/exposure. Usual suspects - high mileage, type of driving, etc.
I doubt it. If wheel bearings are vibrating I don't think they're mechanically forgiving enough to tolerate being out of spec like an axle. I think they have very limited lubrication, they aren't sitting in a huge cavernous supply of grease like an axle. There's more ball bearings, less grease, in a tighter area that's not designed for any play or articulation like an axle. They're not going to click for 50,000 miles like an axle but still work fine. They're going to get worse quickly and fail. I doubt they have some phantom vibration unless it's escalting over time.
I think Fairtax (username) had a troubling vibration on his EJ vehicle that he couldnt' figure out for years replacing multiple items. He ended up accidentally repairing the issue when he replaced....i think it was the steering rack...for some unrelated reason. If you can find that ancient thread, that might be worth looking at. Fairtax 4 me or something along those lines.