An end mill (flat) might work better (two flute), your ball end will always leave tooling tracks since the part that's cutting deepest it the apex of the ball.
I get the same on aluminium but I find an end mill does the job for engraving with a finish pass using a 50% overlap and a minimal depth cut gives an excellent finish.
I've also used bead blasting (takes about 60 seconds for a three inch dia piece) and that gives a nice satiny (sp?) finish and gets rid of the tool traces. My bead blaster uses water though, I'd immagine on wood you'd not want to use water. You can get bead blasting kits dead cheap- all you need is a compressed air line, or one of them portable compressor thingies- looks like a two foot sphere with an electric motor underneath(again dead cheap).