It was already stated in :re that Eto and Shachi are one of the most powerful Ghouls.
Anyone who has read the series could tell both of them are one of the strongest ghouls introduced. In no way it means Shachi is on Eto's level. He wasn't portrayed as such or was said to be.
And I don't think that a crazy Half-Kakuja Kaneki would have performed better against Shachi
He would have more speed, durability and strength. Shachi would have much harder time against Centipede.
Shachi isn't definitely one you should take lightly...
When did I ever take him lightly? I placed him as fifth in my list with Tatara, Yomo and Amon possibly being as strong as or stronger than him.