Obito can control juubi alone.

[~Sovereign~]

fail thread

obito is struggling to control the jubbi, even with madara helping him

if obito becomes the juubi host then no one knows but still fail thread

obito summoned the gedo mazo and couldve been underrating the power of the incomplete juubi

just because someone says they are gonna do something doesnt mean they will get it accomplished

 

[Lucci]

You have some good points, but Obito had no choice but to revive the Juubi as he had already reached a stage that far into his plan, so there was really no going back for him. Also, even though Madara already explained to him how to control it, there is no way he can guarantee to control something he has never seen/dealt with before. He can only go by what Madara told him and hope that he is able to control the Juubi. It was also stated in the manga that the Juubi is becoming more difficult to control as it transforms. This is while both Obito and Madara are trying to control it, so therefore I kinda find it hard to believe at this current stage that Obito himself would gain command over the Juubi.