I'm curious, did you use fdisk (old DOS app) to see if it's simply the partition table? I once had a guy lose a drive and all he'd really lost was the partition table. I used another OS's equivalent of fdisk to re-write the partition table (based on knowing what his block size and volume size were) and all the files were intact without any recovery baloney.
I ran GetDatback but nearly at the end of the scanning I got error messages. Something about I/O Error.
For what it's worth: I/O errors, which I for an internal drive would interpret as a drive failure, have also been a symptom for the aforementioned enclosure failures. In those cases, the drives themselves were just fine.