I wouldn't say they are defective but not all shoes are created equal. I tend to stick with Wagner or Raybestos when it comes to brake shoes or pads. I would call and tell them your concerns and see what they say. If you're not comfortable with the amount of lining then don't install them. Most of the wear is probably going to be on the back shoe so maybe that's why it's thicker. I've never had an issue with Rockauto when returning parts if you want to try another brand.