No time to research this thoroughly just now, but you do not need the DBA role. If you don't wish to follow the guidelines in the other links, or if they don't apply to your DB version, then probably, at a minimum, something quick and dirty like...
grant select any dictionary to <myuser>;
grant execute on dbms_workload_repository to <myuser>;
should do the trick. Also I saw a mention of
grant advisor to <myuser>;
so that may be required for certain bits of the report -- not sure.