We've seen in the most recent chapter that Obito's technique could easily be overcome by Kakashi and literally anyone else (why Kakashi came back out from his dimension I don't know).
To me, that shows that Obito never anticipated anyone overcoming his defense (why would he?) which leads me to believe that he has no other defensive techniques capable of fighting with. The very core of him being so successful as a shinobi has been his ability to teleport and to turn intangible.
With this as a reality now, how can he fight when they know how to defeat him? Just send over a shadow clone to fight stab him every time he turns intangible and that fight is over! Plot requires him to live unfortunately.