In my case, it was usually the rear tires getting the abnormal wear--the car would still track well, and the wear across the tread could be even on front and back, but something off in the alignment would cause that abnormal wear that resulted in the "highway growl". The wear is uneven on each individual tread block. Hard to describe, but the pic on the left kind of shows it. The edge of one side of a block is higher than the other.
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What I've noticed most, however, is that the noise gets louder after a tire rotation.
And yes, definitely--if others have complained on Tire Rack about the same wear/noise issue, then that's definitely a problem.
I have found on my cars that alignment can also be slightly out of spec and still look/feel OK. I try to make it a habit of getting an alignment after each new set of tires. Nice thing, too, is that our local dealer offers a coupon for an alignment that is very competitive ($79 is about what it costs all over town, and they match that), so I get a full suspension inspection along with it when I go in.
When I was short on cash several years ago (post 2008-2009 economic bust), I did my own front toe-in/toe-out alignment. The prior set had worn quickly on the inside edges. I had the factory specs on hand, with one limit being at 0.00 for toe-in. I rigged up two yardsticks with rubber bands, and proceeded to measure the insides of the front wheels at the same spots, front and back, until they matched. I tweaked the toe-in via the tie rods, and never had an issue with it--the new tires wore evenly.