Many times we see this behavior on certain machines but not others. It is a hard behavior to pin down.
Sometimes it is the motherboard, the chipset actually, or the chipset driver
that is not playing nice with the particular external.
Also it can be the external drive itself, or the data cord, or the USB port that results in a transfer fault. You can test for this by plugging the drive into one of the rear USB ports that are connected to the motherboard, try all the USB ports, try a shorter/thicker data cable.
External drives that do not have a power supply and are powered only by USB are notorious for this. Some work better than others, even within the same model.
I run Windows 7 and my external hard drive will run constantly if I let it, and I have not made any changes to my selective suspend settings from default. I believe your issue lies with your hardware.
The other thing I noticed were your 10 hard drives and RAID array. I can't help but wonder if that might have something to do with it.