IMO, I think Sabo is stronger than DD, so I can see him stomping Law.Your scaling has to be wrong because by your metrics:
- Marco could Low Diff Doffy
- Sabo would Stomp Law
- Law could Low diff Ivankov
All of these assumptions are unjustified and can be easily contradicted by the Manga
In case you forgot, DD low diffed Law until he started getting help.
I hope Marco can low diff DD.
People underestimate Magellan and Ivankov. I want to say they're stronger than DD, but I have nothing but my gut to back that up.
Magellan was a beast and if Oda doesn't reintroduce him, then he would be wasting his potential. We don't know if he had haki, but it's not like he needed it at the time.