It seems that when it comes to reporting on opt outs, Eloqua typically uses global unsubscribes or "Total Unsubscribes" as the key results metric.
Unfortunately, this doesn't tell us how many people opted out of a specific email group on a campaign/email basis. At our company we have three different groups, with marketing, transactional and service emails split out by audience and preferences. Sadly, when I come to report on how many people unsubbed from these specific groups, I am unable to do so. I have tried running the report "Email Unsubscribe Overview" but the results are not displaying. I have also tried creating a segment, but attributing opt outs to a specific email is not possible, so it's not accurate. It would be great if we can get this set up.