I think I got you a bit farther than you were...gave you a couple of new calcs for time duration for the Agents based on their log-in/log-outs.
However, in order to get to 'chats per hour' and 'chats per hour per agent' you'll need a lower dimension of data i.e., actual chat session time frames by their respective IDs and Agent IDs just like you have it laid out now in terms of data structure, but with more detail and additional timestamps for the start of the session and end of the session; not just the span of time that the Agent logged in/out.
I hope it helps you get started. If it does, please mark as correct so others may find it useful in the future. Thx, Don
2018.1 version attached.
Sharable Chat Dashboard.twbx 515.5 KB
The linchpin was LoD FIXED. It allowed me to create a virtual view that averaged the difference between time stamps with the same session ID.
From there it was a simple matter to sum the sessions in a given day.
Glad to have helped! D