The first thing to consider is that W2012 R2 is not supported as a Disk Agent or a Media Agent. Certification is being done as we speak, and, at some point, the Certification will be done, and W2012 R2 will be added to the support matrix
Sometimes things that are not in the support matrix will work, but, you are pretty much on your own if you run into trouble
For those of us who are acronym-challenged, what is 'IFC'?
Where are you seeing this "(Unknown Medium Changer)"? If you are seeing it in the Windows device manager, then I'd say that is a large part of your problem, and takes it out of the realm of Data Protector, and I would say that your assumption is correct, it is probably a Driver problem
Can you run this command from the MS-DOS prompt on the Media Agent
cd \Program Files\Omniback\bin
devbra -dev > devbra.txt
and send it as an attachment, so I can see if the command, which lists all the SCSI and SAN-attached devices, even sees the library
Finally, you don't have to have the robotics controlled by this system. You could install a media agent on some other, supported, platform, like W2008, for example, configure the robotics there and the drives on the W2012 system