Have you or your organization ever considered using a third party analytics solution to track your Yammer usage and engagement? CardioLog Analytics is a solution specifically designed for SharePoint Online/Yammer and can provide you with numerous insights on total number of posts, new posts, new members, new groups and more.
I've attached a screenshot to give you a quick preview of what a Yammer Engagement dashboard looks like in CardioLog Analytics SaaS. Beyond this dashboard, you can also view Yammer Collaboration dashboards, Influential Users, Popular Threads and Groups.
In the event that you're interested, my team would be happy to provide you with a tailored session. Let me know and I can arrange it or you can simply schedule one here: www.intlock.com/demo