I'm a rookie, but I'll throw this out for whatever it's worth. I have only had slight experience doing this, but when I did it turned out nice and sharp.
First I ran the art through the scanner as BLACK AND WHITE, 1 bit, and adjusted the contrast and darkness to the sharpest setting using the scanner's custom settings. Then in Photoshop I selected 1 bit depth and black and white and highest quality and saved the file. The result was sharp, dark lines which I converted to vector prior to cutting. It's worth a try.