I am unable to log a support case through Adobe (probably my account permissions. I can try through my company). Essentially, providing users with a mass complete action (and updating the dashboard so that you can filter out completed reviews) enables you to be in control of how you manage your own workflows. Some people mark reviews complete as they come in, others, like me, wait until later to mark their review tasks complete. Since it's not required to mark a review complete to proceed with publishing and you're not currently able to do it from the Guides view (where I am already working), it's not a high priority for me. The review dashboard is an inconvenient location. I have to go out of Guides, navigate to that space, find the review, then mark it complete. It's just not a natural part of my workflow or process. So, they sit open for a time. At one point, I had over 50 different reviews to complete and it was painstaking and tedious work selecting and clicking complete that many times.