EPO can be installed on a microsoft cluster. I've attached the clustered install guide for EPO 4.5.
Agent handlers do not actually offer complete redundancy for EPO. If the ePO server were to fail for some reason the clients would still be able to upload properties / events to the handler (assuming the EPO DB was on a remote SQL server and it did not go down) but the handlers do not have a console so you would not be able to make any policy changes or run any reports. Also the repository pull/replication mechanism is done soley by the ePO server itself (not handlers) so you would not be able to keep your distributed repositories up to date.