Ok new Developments here!
Managed to successfully catalog a tape containing a full backup, after that job completes, i tried a restore and it failed with the drive going offline, same errors as before.
It would appear the SAS card in use, a PERC 6/E is exclusivly RAID only, and does not support just normal SCSI mode, this seems to be tripping up the hardware/software even though there's nothing else attached.
Procured a plain-jane SAS HBA and now waiting on the new cable (long male sas on each end) and hopefully this'll sort things out!
Oddly, I got no warnings or compatibility flags pertaining to the controller on installation, or use etc.