Ok, so it's normal for accuracy to drop as you play harder songs. I don't believe hard rock will do that much to help accuracy on hard maps, but it might help a bit. Try forcing yourself to relax more when you play hard songs. Most people have a habit of tensing their muscles up when they play songs that are hard for them. Tensing your muscles slows you down, reduces your stamina, and reduces your accuracy a lot. It's difficult to play quickly and relax, but if you can do it, you should see a big improvement.
