Then DON'T PLAY on the higher difficulty. It really isn't rocket science. The higher difficulties aren't just there for the sake of being hard. They are there because it is more like playing the real song by the simple fact that you are hitting notes for every note in the actual song. Sure it isn't real guitar where you may need 6 years, but it should still take significant practice time, or there would be no reward to TRULY feel like you are rocking out/playing something difficult and "closer" to authentic. I have LOADS of fun playing the hardest songs on expert, because I can HIT THEM. I've 5 starred the first like 6 and a half tiers on expert. It is fun to play songs like YYZ, Hangar 18, Laid to Rest, Beast and the Harlot, etc. on expert because I can do it. FUN also scales with how much you put in and what you can do.
Edit: Actually, I've heard that Hard in GH3 is even harder than it was in GH2. You do a lot of the same solos/riffs as expert (doesn't really effect me, as I played the demo and 5 starred everything on expert due to the insane amount of time I've put into GH2). So it looks like you are out of luck on this one. Maybe normal is harder too? Or maybe the game makers just want YOU to get better and you refuse.