Make sure you're using your USB 2.0 connection at Hi Speed without a lot of interposing hubs.
Hook it up directly to your Mac to see if you see a difference. You will.
I had a similar issue. My computer has USB 2.0 ports but evidently, it is implemented like a hub of sorts and having older devices like a keyboard, mouse, camera, etc was forcing it to USB 1 speeds.
So, I bought a $15 USB 2.0 card and kept all the old slow stuff plugged into the motherboard ports and the iPhones, iPads and a USB hard drive I've since acquired plugged into the new card and holy freaking crap it was like night and day.
It went from dreading a sync to laughing as the bar flew by.
My back ups are slow too, dread doing them, hate not being able to use my iPad lol!
What is a USB 2.0 card, do you have a link?