I see it like on your image. With only a few variants the current layout may be ok but if there are many variants with several attributes and you want to add or change all fields, it appears overloaded to me. My suggestion is to add a space between the variants or a line with dark color. But the best would be to style it the same way like as the following plugin does it: Order Minimum/Maximum Amount for WooCommerce.
And i think it would be even more better to move the fields down into the product data block, for variants each into the corresponding tab, for a clearer interface and like other plugins do it too.