[mrweasel]

>Some of the larger website builders/hosting , e.g. Wix don’t even give you access to server logs.

I don't think it's unreasonable to require them to provide you some sort in insight into your traffic data in that case.

You can to promotion tracking with just log parsing, depending on how your system is built. There's a large number of sites that handle that by simply having unique URL for each promotional partner.