Is DFSR designed for use for Disaster Recovery?

I've just moved away from a DFS-R environment because of the very reason you described above. Locked files are impossible to deal with and causes all kinds of conflicts especially if both servers are being used like a proper failover (so users are hitting both servers at once).

To me, DFS-R is decent for replicating over WAN/VPN connections to remote offices and not as a DR solution. I highly advise getting some sort of shared storage and using Failover Clusters which have improved quite a bit in 2012 R2 (I'm still on 2008 R2, but it's served us well so far).

It is not designed for DR. Not in this way - in this case the user is the problem. I am not sure anything will handle that nicely.

DR also is a crappy scenario it will happily replicate a virus encrypting your files (or deleting them).