The reason why Sasuke have not shown in this chapter is because next chapter sasuke is going to play an important role against Rinnegan Madara with his new body.This is similar in Chapter 656 where sasuke was not seen when Edo Madara was undergoing his plan to become mortal then when Madara become mortal Sasuke appear and almost solo him in two ocassion,if it was not for plot no jutsu the war will have ended .Kishimoto just waiting for Madara to get a worthy power up for Sasuke to develop his own power to show his viewer the true power of Sasuke.
Madara fighting the tailbeasts was just to show Madara body duality and also to show why he become mortal because he very difficult to kill as an edo tensi because he can heal with hashirama dna or repair parts with random zetsu he can called upon.Stay tune,Sasuke will have a counter or a power up that will make him fight Madara with or without senjutsu dna.We donot know what EMS have to fully offer and Madara mention about Sasuke Chou sharingan which mean something important for his power up later down the series
Madara fighting the tailbeasts was just to show Madara body duality and also to show why he become mortal because he very difficult to kill as an edo tensi because he can heal with hashirama dna or repair parts with random zetsu he can called upon.Stay tune,Sasuke will have a counter or a power up that will make him fight Madara with or without senjutsu dna.We donot know what EMS have to fully offer and Madara mention about Sasuke Chou sharingan which mean something important for his power up later down the series