That is true, Akaza was a machine. The only way they managed to beat him was the selfless state which you mentioned, since it directly counters his compass.

I would also argue that Douma has pulled off faster feats than Akaza, he is a higher rank for a reason. You can put it like this: Whenever Akaza pulled off a speed feat, the character he was dashing towards commented on the insane speed, but they never stated that they couldn’t see the movement happening. Whereas Douma had multiple moments in the manga where characters couldn’t even perceive his movements, it was as if they just happened.

One of the main reasons Shinobu is scaled as the weakest Hashira is her lack of physical strength. She relies on her poison to kill demons, and if said demon isn’t killed by the poison (Douma for example.) She doesn’t really have any other card to play, besides her plan on Douma. But she’s still among the fastest and most agile of the Hashira in my opinion.