Just about everyone in the ser2net thread (Share Z-wave dongle over IP (USB over IP using ser2net / socat ) guide) would have a use case for it as well.
One of the biggest issues with ser2net, which the Event bus situation solves is the lack of signalling between ser2net and the Zwave binding (or any other system). What can occur and occured frequently for me and others, is that if ser2net looses connection and it does, the ZWave binding does not know about it.
That causes all sorts of ZWave issues and the Zwave network then breaks. You must restart it all , manually, or automatically if you’re extremely advanced and can script it.
The advantage of the event bus is very simple. Two discrete networks, operating independently, no bindings to restart. Should one of the master/slaves fail, they restart themselves and come back up, leaving the rest of the network to function (ie the other node that hasn’t failed).