I think it's commendable to keep seeking a solution via community input, instead of just reaching for the nuclear switch.
It makes sense to raise curation rewards up and tweak the curve, but as @whatamidoing says:
In the end there is always this paradox between the ability to self vote and the ability to create multiple accounts, it seems that if you try curb one, the other will be abused.
I'm not sure any %'s or curves could have enough impact to reduce multi-account circular voting.
Ned discussed in a recent video SMT having the account weighted voting option, this would help to an extent but unless accounts can be tied to 1 real life person, it's still going to be open to abuse. This option also doesn't seem to be coming here anytime soon either, and so is perhaps a moot point in this discussion.
Do I have anything positive to contribute on this one? Only that I'm with @steevc on continuing, despite the shenanigans I see from some of our largest accounts / biggest voices, to try to build Steemit into the place I want to see.
Cheers