If you guys are trying to beat banding with profiles and noise then you are getting lucky to get anything at all. Banding is a function of line screen over resolution. How long or large is the area that is banding? A gradient I assume (vignette is a little vague)? The problem with these digital presses (I'm running a KM6501 right now) is that they run a very high line screen with not that high of a resolution. This kills your levels of gray. I may be running a 200 line screen but my drop shadows and gradients are very poor. Depending on what RIP controls you have the only thing you can do, with a traditional dot, is turn the line screen down. I can go from 200 to 150 and the banding lessens, but the pictures grain up a little too. Not bad though, 150 was the standard for a lot of offset for many years. If you can do that, it will help a little.
I have a 6501, and yes it does band as well. I have been able to fix most of my issues with adding noise, but it has to be the right noise. I always use monochromatic, it works the best, also if the gradient goes out to white you should adjust it so that it doesn't, make it end at like 2% instead - you can mess with the number but it sometimes helps.
As with other comments on this subject it certainly does help by turning off profiles and turning a illustrator / indesign gradient into a Photoshop Tiff (but this is not always a option). So this must be the RIP interpretating the data which you are sending?
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