I have the same issue but I think it's less of an issue of the blade/etc causing an abrasive pattern. I think it might be cheap Chinese/etc. windshield washer fluid and possibly the addition of amonia or other chemicals that are causing the issue. It just happens to follow the outline of the wipers because the blades are washing it off and the chemical/fluid is then resting on the rest of the windshield and doing it's damage.