The big problem is that ebay don't care. On top of that, trading standards and the government know all to well about ebay and don't seem to care either. This generates the "if you can't beat them, join them" attitude, even though it is the wrong thing to do.
I spent time chasing people on ebay a few years ago. Our company designs were used which we had done on behalf of certain brands. We used to get in touch saying we were going to report and we get a load of abuse back. We pass this info onto ebay, sometimes they act and sometimes they don't. It ended up a daily check on ebay and next thing we new time was filling up with trying to fight a losing battle. Unless they care at the top of the chain, we can do very little and it becomes "almost" okay to operate like this on ebay.
There are designs that the OP has that corssover onto brands that I currently print for, so indirectly affects me. Am I going to kick up a fuss...... wasted enough time in the past to know it will be further time wasted.