Exporting Dashboard (PPT, Excel, .csv)

I am able to export data from a dashboard tile within a dashboard that is shared with me.  Perhaps it has to do with the settings for the users in the workspace or at the tenant level.  Have you gone to the admin portal to investigate the settings?

As for you last question, the ability to export to PPT or excel:

The service has the ability to export to PPT.  If you go to the REPORT and not the dashboard, under "File" menu you will see it.  It is a preview feature so if you don't see it, don't worry, you just need to turn on preview features under settings.

There is also the Analyze in Excel option, but this just creates a connection between a power pivot data model and the data model in the service.  If you want to work with the raw data you need to export the csv.

However, with all that said, I will point out that PBI is a visualization tool, and the service is for collaboration.  It is not meant to be a file sharing service.  If you want users to be able to work with the data, I recommend using an R script in the query editor to write the data to a csv in a shared folder, that way you can let users work with the data separately from the PBI experience.  Be cautious here though as this may lead to fragmented data marts and not "one version of the truth".