Avoid duplicate product while using variations
It sounds like you reference multiple products per display node, so adding that relationship results in multiple rows. A real easy solution is to filter by the delta value from your product reference field so that only the first referenced product results in a row being shown. Ideally we'd add another filter that let you filter by the default delta value, as that can differ from 0 if altered via code.

The filter you're looking for should read something like: Content: Product (field_product:delta) and you should set the filter value to 0. No need to expose it.