Bevel and extrude looks bad

Ive used the 3d extrude and bevel with some lighting on some type which I have then copied and stacked one on top of the other but my finished result is less than desirable. As you can see the highlighted parts dont look smooth but look sort of have vertical lines.   I have my anti alias on and I have raster setting set to high.  How do I fix this so it looks smooth please?      This image is magnified to 200% but even at 100% it doesnt look good.Image may be NSFW.
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