Dataguard for eBS

Now running eBS 12.2 on premise, I'm reviewing eBS on Cloud for future running of Production instances and I see Dataguard be part of a/the Cloud solution (when migrating an existing on-premise to Cloud).

That 12.2 environment has RAC but not Dataguard. Depending if the choice is taken to migrate to Exadata, to 2-node RAC or even single node, my question is this: is the Dataguard option mandatory for Exadata only ? Is the role of Dataguard to replace the current backup system (RMAN based) ? As RAC is already providing a solution for Single-Point-of-Failure.