You can export worklogs to Excel with the Better Excel Plugin, and report on the exported data.
The particular use case you mentioned time-spent per user per issue per month is available with one of the default templates, called worklog-report.xlsx, that creates a pivot table similar to this:
Hey everyone! My name is Sarah Schuster, and I'm a Customer Success Manager in Atlassian specializing in Jira Software Cloud. Over the next few weeks I will be posting discussion topics (8 total) to ...
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