Nice to see a serious, courteous discussion about this topic. I recall the same issue being brought up back when the game first came out, and it seems it hasn't quite been resolved to a lot of people's satisfaction.
To me, it seems obvious that Mono should just be separated and given its own scoreboard. While there may be other possible ways to deal with the issue, this one seems the simplest and most resolute. Everyone appears to be in agreement that Mono plays differently than the puzzler ships. While many think Mono is underpowered, some think it is overpowered. Separate scoreboards should satisfy both of these groups. If they are so different, why bother keeping them together anyway? I can't see why anyone would have a strong opposition to split scoreboards.
I play almost solely Ninja Mono. While I can probably get stealth/clean finish on easier songs in one or two tries, the songs I prefer playing are a bit more challenging. For example, I only recently managed to stealth a song I'd been playing intermittently for over a year now (it's listed as my most played song with ~130 plays). You could say that I suck, but I'm the only one to have stealthed this song. Personally, I don't mind terribly when a few Pusher or Eraser players have scores that I can't beat, because I know I'm not really competing against them, and take comfort in having the highest Mono score posted. What does bother me is that on any popular song, all Mono scores are completely blocked off the scoreboard.
Now you could easily say to me "try a puzzler". Two responses to this. First, I actually did this once. I surfed a song in Mono, got a max score, took the throne. Not long afterwards, I was dethroned by the Eraser player I had taken it from. Only a few thousand points ahead of me, I decided to try out Eraser. After a few tries, I was able to take it back. I ended up playing with Eraser a bit more on similar songs where my perfect Mono score had been bested, and did okay. I'm throwing this out there to address all the "Mono is too easy" comments. With little practice, I was able to beat perfect Mono scores with Eraser. Secondly, I simply don't enjoy the puzzler ships as much. I find that Mono allows me to focus on the song more, and just enjoy surfing it. Puzzlers, as has been said, are more cerebral. The play style is completely different.
IMO, the main issue with Mono is the score cap. I suspect that the only reason I hold any thrones at all is that the songs just aren't popular enough to draw the attention of decent puzzler players. Yet I think I have earned those titles, and feel I am a very strong Mono player. However, I think that mediocre puzzler players could probably beat my scores in a lot of instances. Again, we're sort of left with the problem of comparing apples to oranges. How good at Mono should I be in order to compete with those who are excellent Pusher or Eraser players? The sad fact is that even the world's best Mono player is going to get stomped by them due to the score cap. I'm not sure balance is really feasible, however. Separate scoreboards just seems like the simplest and best solution.
