Individual Score Achievements
Got the Satch Boogie and Assassin achievements last night and wantted to confirm that they can be done in quickplay and career mode. I did the drums in quickplay as I hadn't bothered to finish the career and did the guitar on the setlist.
Also, both of these can be done on Hard difficulty with relative ease. Hit around 245k on Assassin with only 97% on hard and 222,900 on Satch with 98% even with blowing half of the slide section.
I'm rather disappointed that they can be done so easily....
As far as Beat It goes, the vocals system probably makes it the hardest to do individually.