This fight is the perfect moment for humanity to win and secure their survival while also making the gods think "oh no, we have a problem, humans please help" when Odin's plan still unfolds in some fashion. After all, pseudo-Odin is only a copy of consciousness manifested through Gram (chapter 97) but he possesses all of the other weapons inside him too (chapter 98, page 4 & 6), so him dying doesn't matter if Odin can escape with Chaos, Satan and Ymir.
NB: Gollnir was mentioned in chapter 88, page 7 (the forbidden book that Beel found, "Book of Gollnir")
Also, it'd be very funny if the Anubis-Rasputin fight never happens because the authors and artists just couldn't decide on Rasputin's design.