You can try a custom driver which polls periodically the repeater and shows the online/offline to the hub status.
Look for the link in the 'Zigbee Repeaters' section in the second post.
If any battery-powered end device uses ut as a router, you will see it on the map - in my case it is just one device.
Sort the Zigbee details page by 'Msgs' column - if your hub is running for more than 3 hours, all devices showing Msgs = 0 are suspicious for being offline for some reason.
