I've got a Xerox 700 with an external Fiery RIP, and when I print gradients there's seems to be a pronounced banding/stepping on the gradient. it's noticeable enough that it looks like two different colors were applied, instead of a gradient to white. i've also tried the gradient set to 0% opacity in InDesign; same result. I've adjusted the print quality settings up -- turned on image smoothing, set image quality to best, text/graphics quality to best and adjusted the printer screen mode with no luck.
we're about to our wit's end with this machine.
Not sure if there is an image noise option on your front end but on our Creo for the iGEN we use image noise on gradients and it seems to help out a lot.