I dont think they can defy edo tensei under orochimaru i dont think oro let them to do that but even all hokages somehow escaped from it still they dont match for juubi
Orochimaru didn't put that binding seal into their heads. And as you can see clearly, this Edo Tensei is the same as the one Kabuto used. Compare this Edo Tensei and the one he used in Part 1.
there is also a chance that Oro will use them to defeat Madara and Obito cos I dont think that Oro wants to be stuck in Infinite Tsukuyomi maybe after that he will put them to rest we will see what Kishi has in his mind