I do not know about other large sites, but a set of diagnostics on one of our polling engines is now over 1.2GB in size.
This is becoming expensive (in time) for me to gather; fortunately I have many 10GB network interfaces to speed the upload, but it still takes me time to babysit the zipfile generation and then the upload.
There are times when diagnostics are required, but the current diagnostics gathering process dumps a whole bunch of data into files that can be barely relevant to the reporting of a UI issue.