Hi @mwrobel,
Thanks for posting your question!
Have you considered using the Issue Cycles approach?
See Issue cycles documentation for more details on setting up custom cycles.
Once you have imported the issue cycles (where you have grouped all the statuses you want to consider counted), use the measure “cycle name workdays of resolved issues” to display the workdays. Or use the measure “Average cycle name workdays”.
Here is another community post about the issue cycles, you may find useful - Add values in the fields - #2 by Marita_Norvele
Best wishes,
Elita from support@eazybi.com