TL;DR: Is it possible in any way to get access to the usage information on a per site / per site collection basis and include external users?
I'm trying to get some stats for SharePoint usage, but I'm really struggling. It seems audit reports aren't available programmatically to get detailed information. The Power BI Office 365 Adoption Preview only provides summarised data and doesn't provide the information I really need as far as I can tell.
Ideally, I'd like to see usage on a per site collection / per site basis. And I'd like it to include external participants. So far, all the information I've seen only includes internal users? Does that sound right?
Any information anyone can provide would be greatly appreciated. Thanks.