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.
NO. Scuffing would be equal on inside and out as there are equal forces on both sides.
Get the worst tire off for a good inspection. Post pictures of the worst area from a few different angles. May as well post the brand, size, pressure you run, age and the DOT manufacture date code.