Can't mount primary HD, Disk Utility shows Invalid Node Tree Size There are similar lines of questioning in the forum, but few valid responses. Apologies for reposting. I've searched for hours on end...

I'm a tech consultant (software, not hw) helping my relative out with a problem on MBP 2011 running Mavericks.

One day - it failed to startup &amp; he was brought to diagnostics / language page. Disk Utility verify sees problems with Invalid Node Tree size. Repair says it can't be repaired. 

fsck tried from single-user mode, nothing. I don't even know if fsck will work on a  volume that is not mounted?

I tried creating a mount point (mkdir /Volumes/newmount) and mounting the drive there, no luck. Mounting from Disk Util also fails.

I tried creating an image of the drive (actually...all 3 of the drives...Mavericks I guess has an EFI and 'Restore' partition). The image failed to mount on an external HD. 

I have purchased DiskWarrior - that's my next step. The last backup was "in August" which actually meant "June of 2012" upon investigation into his TimeMachine backups. He's got family / baby photos and videos and is desperate to recover. 

Is there a way to remedy the 'Invalid Node Tree' issue? For instance, if I run migration assistant &amp; migrate the volumes from old to new, will a new 'Node Tree' be created for me on the new HD? Is there a different approach I can take to making the disk image copy - just isolating the 'Macintosh HD' to improve my results?
Use DiskWarrior. It is exactly the purpose of the software to fix such errors.
If DiskWarrior can't solve it. Use something like DataRescue to get the data, then reformat and reinstall.