As I tell all my clients, The problem with doing seps from a raster file that has tint's tones, gradients & halftones, is that I will give it a 55 dpi pattern to reproduce those and that will apply itself to everything, including fine lines, text edges, even the tints area edges......
at 55 dpi no matter the files resolution it is brought doen to about 110 ppi.
It would just be faster for me to redraw it vector then mess with it. and I hate producing stuff that looks like it was printed by a hack
the client will always complain about the final product and not equate it to the original crap !