At present I believe there are a number of permissions that have dependencies on other permissions eg. ONLY enabling 'Real Time' under Advanced Reporting Access won't grant access to the Real Time report(s), as an Admin user you have to then second guess the dependencies .. which I haven't yet worked out for granting someone just Real Time Acess. It may not be possible to grant a group specific permissions the Admin requires, however showing the dependencies should make it more transparent.