The best way I know to make that sort of repair unobtrusive is a 'finger' patch. Ideally you use an offcut of the same wood, but take the patch pieces from places where the grain spacing is wider. Be sure to match up the cut offs to their proper places, too, so that the run out matches.
The idea is to cut in a lot of short pieces that are as wide as the grain lines, so that the glue joints along the grain all fall on the hard, dark latewood lines. The ends of the patch pieces are cut off at an acute angle across the grain, not straight across. You start from one side of the blowout, and work your way across, making sure that the ends of the patches don't all line up in the same place. You have to have a really sharp knife with a fine point to make the cross grain cuts, or the glue lines will show. Use Titebond or HHG, not CA, as the water based glues will shrink and minimize the glue lines.
This sort of blow out is sadly more common with WRC, as it's more brittle than spruce. A sharp, new router bit (preferably steel, and not carbide), run on high speed, with a light cut, and advanced slowly, helps. Wetting the surface with a light spritz of water on the 10 o'clock and 4 o'clock quadrants, where the bit is running into the grain, helps a lot. I have heard of luthiers who buy a new router bit for each guitar to minimize this: it would probably be worth it, given the cost and diffculty of the repair... ;(
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