You can add your comment and suggestion on this thread.
https://support.viki.com/hc/en-us/community/posts/360000016547-Regulate-Reviews-and-Ratings
If you want to read pros and cons of various suggestions, you can go here:
https://discussions.viki.com/t/why-are-people-leaving-reviews-on-dramas-not-watched/9852
In my case, I don’t agree with viki measuring the viewing time. Sometimes we may have watched the drama elsewhere, especially if it’s not available in our region here at viki.
My suggestion is that at least the drama should have completely finished airing.