If you have a USB/SATA caddy, and you can boot Linux or Ubuntu on your PC/Laptop, then it should be able to see the drive. That's the easiest method I know. I've done this in the past to salvage data from my drive. With Ubuntu, it should know if RAID was used. This was from an older, NAS, the DNS-320.
P.S., Like what you experienced, I had my DNS-320L behave in the same manner, power LED flashing, but no drive activity. Luckily, it was still under warranty, went to the repair center and got a replacement unit. I had only one drive, and dropping it on the new box, it worked. The system didn't ask for the drive to be formatted.