Simply countering the Rin'negan's techniques isn't the issue but chakra pools would also have to be considered as Kakashi rightly stated. Jutsu such as Chou shinra tensei, Chibaku tensei or using multiple paths simultaneously [for each jinchuriki also] would have no doubt taken tremendous defects on Obito looking at the tolls taken on Nagato. Obito's objective with the Rin'negan was to resurrect the Juubi, nothing more.
@Bold: In actuality those things would have been tasking given that Obito was:
-> Maintaining control over both the Jinchriki and their Respective Bijuu
-> Supplying them basic Sharingan functions [ability to anticipate attacks]
-> Supplying them basic Rin'negan functions [linked vision]
-> Maintaining the Gedo summon
-> Utilizing Kamui
-> Utilizing the Outer path chains
-> Initiating Jinchuriki transformations
All these things would have been consuming his chakra tremendously; and how would utilizing the paths aid him in any when when they can easily be anticipated by team Naruto? First of all, focusing on individual opponents leaves him open for other attacks. Obito had no intentions of getting involved in the fight as he was already using up too much chakra in controlling the jinchuriki and moderating the battle especially because the full Bijuu were able to breech his control. Also the Rin'negan paths do not require any training but simply that the wielder possesses the doujutsu. It is highlighted in the fact that Nagato as a child had access to it's power long before learning basic Ninjutsu. That scan of Madara stating he would teach Obito Uchiha Kinjutsu and Rikudo Jutsu doesn't necessarily have to refer to the Rin'negan as all 'Rikudo Jutsu' do not hail from the Rin'negan. DSM Kabuto was also able to produce these jutsu, not wielding eye techniques of any sort solely implying that the Rikudo may have had special jutsu outside the Rin'negan's potential which may have also been deemed as 'his' jutsu.
