This is the same issue that happened to ALIEN where it was too hard to balance it due to how the map as a whole was built around. It's either you have to set it up too high in order to make the hardest sections more comfortable or you just set up something in between to find a balance with both sections. Unfortunately you cannot have variable ARs, so I think the current one works just fine.I don't think you can really compare it to ALIEN where it's just dumb to use anything else than AR10 considering how crazy the map is and that the players actually able to play it can play slow stuff on AR10 without any problem (just as if they were playing HR pretty much).
I slightly agree with the AR on Haruto's difficulty, although it's not that much of a deal unless you are trying it to DT it.fk he knows
Edit: welp that answers your question I guess Monstrata, of course I'm considering DT lol, it's fun as hell but the AR gives me aids it's just way too high for no reason :/ Even AR9.6 would fit better on that kind of spacing man...