Damn, man, will definitely rework the difficulty. I think that there are a lot of things I wasn't able to do. Next update, there will be lots of fixes, i promise :)
I also tried the most difficult, in the easy mode I usually get around 2900 for the main song (influence), in the most difficult I got around 2700, so yeah the difference should be more significant.
I just tried again the easy mode (playing influence), I got 3800.... one day later I improved so damn much lol...it is up to you to tune it, not sure what is the best lol