There is absolutely no benefit of using Private Node, cause that means you need to do granular permissions. Instead, if you have a staff forum for example, change the permissions on view node (in the node tree) for Registered users to Revoke, then explicitly set the view node permissions for your staff secondary group as Allow. There is no real point in setting the other permissions, as long as you use inheritance correctly for the other groups.
When you add new staff members, just make sure they get added to the staff group as a secondary group.