What Could Cause This Wear Pattern?

There are large wave sections of the tread's edge completely wiped off in large portions. I understand my pics aren't the best but it can be seen.

 

Exactly. I'd hate to put a new set on only to have it happen again and spend double in the long run. I was thinking bad belt due to a strange vibration I'm dealing but wheel bearings could cause this too? It's only on the two tires opposite or each other on the same axle. Wouldn't all four tires on the same axle do it since they share the same hub/bearing?

 

I used this procedure:

"MOUNT HUB AND TORQUE BEARING. Lubricate the outer bearing and lay it and the fastening hardware on a clean towel. Carefully slide the hub onto the axle spindle until it bottoms out on the shoulder. Be sure the hub goes on straight. If it binds, remove it and inspect the seal for damage. Holding the hub with one hand, quickly install the outer bearing and spin on the large adjusting nut, tightening it according to the specification for that particular wheel end. Manufacturers typically recommend a torque wrench and dial indicator to properly set the bearing tension. Most mechanics, though, rely solely on a torque spec. When working on a traditional heavy-duty axle with a double-nut fastening system, they’ll crank down the adjusting nut to 200 pounds-feet while constantly turning the hub. Then they will back off the nut a full turn and retighten to 50 pounds-feet, again while turning the hub. The adjusting nut is then backed off the nut 1/16 to 1/4 turn to accommodate the locking ring or cotter pin. The outer, or “jam” nut is torqued to 250 pounds-feet to 350 pounds-feet, depending on the style of locking hardware. Fill the hub cavity with lube."

 

Still unclear how a shock could cause that to happen.