What would be the best approach to segregate data in a single tenant? A set of users (within the tenant) needs to have data segregated from all other users. Could this requirement be achieved through AD structure?
In O365 you have no control over where the data resides. It is all controlled by permissions. If you require the data to be isolated from other users and tenants on its own servers then you will have to setup your own infrastructure for Sharepoint and Exchange.