I seriously doubt anything is wrong with your alignment. It is "normal wear" for tires.
As you drive on the road, roads have crown. You adjust the steering wheel (albeit very slightly) to compensate for this crown. This creates a slight bit of scrub. When you go around a turn there is a little bit of scrubbing that occurs on the tires. As your suspension flexes over bumps/humps/the bouncy stuff on bridges from the seams/etc, or when you go around a turn and the car leans, it changes the camber (again albeit very slightly) and the tire will scrub a little. Over the course of 5000, 10,000, 15,000 miles this little bit of scrubbing adds up.
Generally, the feathering like that is caused just by not rotating your tires. Regular tire rotations promote longer tire life and more even wear for this reason. more even wear across the individual tire, as well as even wear between all of the individual tires. All cars do it.
With non-directional tires I always use a "modified X" rotation pattern... I will bring the rear tires straight forward. Then switch RIGHT and LEFT tires when they go to the back. This REALLY helps a lot to "even out" the feathering that occurs much better. But with directional tires, it's not really an option.
I wouldn't worry about it. Like i said, with street tires it seldom if ever will cause a vibration issue. Mostly the tires just get noisy. Our cars are noisy as hell anyways so it's not hurting anything lol. With mud tires on trucks however, the tire tread and lugs are much deeper and definitely can cause a vibration. Once they get bad enough it's almost unbearable to drive and the tires are trashed.