Vibration at 75mph. Bad hub?

I would start with your tires, sounds like a possible flat spot or out of balance tires maybe even choppy edgewear causing road noise and vibration. With my experience with wheel bearings its more of a constant whining/moaning noise rather than a "womp" noise. Usually itll get louder as you drive then disappear when u make a turn.(thats if its a bearing) i've also had them give me a vibration that can be felt in the floorpans. But like i said start with your basic stuff give your tires a look over if you have access to a lift or balancer for the hell of it spin them and watch them see if there are any dips or anything on the tires. Worked for a tire shop for a few years and alot of times ppl mistake suspension noise for tire noise. Hope this helps.
shane