I've never used the enterprise version of SeaTools. That's why I posed my answer as a question.
I would think that any virtual drive could be surface scanned by any third party HDD tool. For example, "HDDScan is a freeware utility for hard drive diagnostics (RAID arrays, Flash USB and SSD drives are also supported)".
http://hddscan.com
However, I think problems might arise when you try to diagnose each individual drive behind the RAID controller, as you have no doubt discovered.
FYI, here is a thread which suggests that SeaTools won't give you access to your drives:
http://forums.storagereview.com/index.php/topic/23297-seatools-dell-not-work/
One user suggests that "SCSI Mechanic 3.0 evaluation software" might be useful under certain conditions:
http://web.archive.org/web/*/http://www.scsimechanic.com
http://micro-magic.com/products/SCSI-Mechanic.htm
You can still download it here:
http://web.archive.org/web/20070629003112/http://www.scsimechanic.com/eval_version_download.htm