So tires are pretty much junk unless you're going to autocross the car everyday. I wouldnt doubt that its a helping reason as to why it follows grooves/ruts in the road.
Inside wear is somewhat common on the GXP, they have 18x8 front and 18x7 rear for rim size. Because of the 2 different size tires, its hard to get perfect wear and even harder if the tires up front or in the rear are directional. They will spin the same way their whole life and can wear quicker, also if the camber is off on any corner it will wear the inside edge faster.
Some new tires and atleast check the alignment and you should notice a difference.
