So I guess I have an excuse to use my underpowered hub to experiment cool my devices. I've been very lucky I haven't killed them yet like my nvidia card. At least since its not rosewill, my cheap hub doesn't need a connection to the pc to turn it on.
Sure, as long as it has its own power supply, it can happily drive your fans... I use cheap 10 port hubs with alternative power supplies (3 or 4A instead of the 1.5/2A power pack that originally came with them), but never fully populate them to allow both air flow and to be within the supply capacity.
Cheers