Is it normal for tires on a 5'ver to wear evenly across all threads. Or, because of scuffing and being ST's will the outside threads wear faster then the center. Giving a slight "football" appearance.
Wear to the outside edges would be more likely caused from under inflation. However, like Lyle suggests above, normally you would see little wear, unless you have alignment issues, or are backing/turning tight frequently, such as into a tight turn concrete driveway.