In relation to workflow and backups:
Basically how I work is to have the current work in progress on a drive (which is backed up) then once that project is completed it is transferred to the main archive, which contains everything (and which is backed up) and then save an edited selection to another archive (which is also backed up).
So for the project I am working on I always work from a separate drive (+ it's backup) dedicated to that project and only transfer it to the main archive once it's done. That in fact has saved my skin during this whole debacle as I had a current work in progress on that drive and it had not yet been transferred onto my archive, which was the drive that Mavericks messed with.
The problem was I had just set up that 12TB capacity RAID as a main archive this summer and had transferred my data from my previous archive to that. I still have my previous archive and it's backups spread across multiple drives but unfortunately I'd been so busy the past couple of months I'd not got round to setting up the new backup of the archive as transferred onto the 12TB RAID (which I should have done from the beginning), and which of course I have been working from. So there's a couple of months of work on that RAID array that Mavericks messed with that is not backed up anywhere. That's me being an idiot (setting up that backup was on my to do list, along with many other tasks...). I've just ordered what I need to backup the RAID array, which is my main production drive, once I get it sorted after this mess.
Basically this whole Mavericks incident has kicked me into making that task of sorting out the main production archive, the edited selects archive and the respective backups of them a priority, and reminded me why I shouldn't let my backup routine lapse.
Still, I'll say again I'm shocked that this issue was not picked up during beta testing of Mavericks. Especially as it seems to be more widespread and varied than just an issue with the WD software.
Before I attempt a data recovery on my drive, I will wait and see if Apple come up with a solution. A tech support guy told me they are working to the premise that the drive has not been formatted but that something - sorry if this is a bit vague - something is preventing the data showing up. In other words the data is there, the drive has not been reformatted, but the data is hidden and the drive is displaying as empty. That sounds promising but I'll take it with a pinch of salt. Though I was told that I may have to resort to data recovery, I was also told not to carry out that process just yet. At the moment I am willing to give Apple's engineers a bit of time to see if they can come up with a 'magic bullet' that will allow me to plug in the drives and reveal the hidden data. Assuming of course that that particular premise is correct.
For those going ahead with carrying out data recovery, I'm glad that seems to be working. Alongside Data Rescue 3 and EasyRecovery 11 Professional (for which it seems WD is giving out a license key to it's registered customers) there are a couple of methods I've had success with in the past. The following Testdisk and Photorec have both worked for me.
http://www.cgsecurity.org/wiki/TestDisk_Step_By_Step
http://www.cgsecurity.org/wiki/PhotoRec_Step_By_Step
And one I've not tried but some people swear by is DDrescue. http://www.gnu.org/software/ddrescue/