Sorry for the delay. 

Time based reports and Reports for SLA/average response time etc., is under development right now. I believe your requirement will be met once we implement these reports. 

I do understand that manual Time Entry is a tedious work to the agent. We will soon automate time entry as well. We are just in progress of releasing our new user interface update. So you can expect more updates in the following months. 

Sincerely,

Lawrence | Zoho Customer Support