First I was going to call you a newbie and that shares can vary in weight... then I noticed you are the owner of Suchpool and probably know what you are talking about.
Maybe others can investigate this issue.
I of course understand shares can vary in weight. However this is why I posted asking for others to investigate this, mostly because it's quite late I'm tired and other opinions wouldn't hurt.
He asked how to set static diff on nicehash since it's not supported ..I also wonder since I can't find any hints about static diff on nicehash.
Yes you can:
https://www.nicehash.com/?p=faq#faqs10I know it is not properly static but more or a preferred diff, however it is usually working nice to keep a worker diff around the specified limit.