External hard drives do not spin down and overheat
After studying my problem further, I identified the Newertech Ministack 2012 as the cause of my problem. I had to deactivate Drive Genius' DrivePulse, since this program apparently keeps external drives from going into standby. After doing this and switching Newertech USB3 cables for generic USB2 cables, the drives go into standby, but after resuming from standby the fans remain off. This happens in multiple enclosures. It might be a production problem.