I'd tend to agree with this, but the solution should probably cut more in favor of dropping the floor for sentencing of rapes where the victim did resist than raising the floor for ones where she did. Obviously you want similar sentences for similarly situated convicts. But ideally the criminal justice system should be designed such that a situation like Brock Turner happens more often than a situation in which someone is forced by law to be punished far more harshly than necessary. And we're definitely erring on the latter side currently, not the former.
Is there any particular evidence base to suggest that lowering sentences for more serious crimes would reduce offending for ones classified as less serious? I think this is especially relevant given the public outcry about the unduly lenient sentence given to Brock Turner and the wider question it raises about how society implements punishment for crimes. Brock didn't show evidence of remorse for anything other than "drinking" and clearly didn't seem to accept that what he did was wrong, so can we really consider that sufficient to communicate the censure of society for the crime committed?