Worst part of this outage: paying for a multi-az RDS instance and having failover totally, completely, fail.
Did/does your standby replica in another AZ have any instance notifications stating there is a failure? The outage report claims there were just EBS problems in only one AZ.
Multi-AZ RDS does synchronous replication to the standby instance -- I'm guessing something broke in there. Hopefully AWS will update with a post mortem as they usually do. Lots of frustrated MultiAZ RDS customers on their forums.