I have seven drives connected through a Belkin hub. It works great. Speed isn't as fast as if it were directly connected, but it's not terrible. Wired speeds are in the 5.5-6 MegaBYTE range. This is about half what I would expect, but makes up for it in the convenience factor. Wireless regularly hits 2.5-3 Megabyte, which is better than the 1 I used to get with G. (I can see 11 access points from my dining room, I'm thinking most of my speed improvement comes from running N-only in the 5 GHz range where no one else is playing...yet.)
Since the drives work individually, I'd suggest trying a new hub. I had an off-brand hub in place first and it worked, but it kept "dying". (The lights would all go out and I'd have to unplug the power and the upstream USB port to get it to reset.)
Defnitely recommend a powered hub too...