My first set of Avons lasted 1,400 miles! I do not think bump steer was that big a factor but the 10 or so degrees of toe in certainly contributed to the rapid wear.... Avons should only be used on static display museum pieces.
You kept on driving it with 10 degrees of toe in? That must have been interesting handling and fairly obviously wrong, even to just the naked eye. A top quality PDI as well.