failover works perfectly if you dont have automatic failover. Its the automatic bit that makes split brain possible. Our hyper-v site failover is manual. We issue a command to the cluster telling it which site is active. When the main site goes down we issue command to failover to backup site, when main site comes back up then we issue the return and the backup falls back and replicates back. If we lose comms between backup and main then it sucks to be at the backup site (as we dont issue the failover).