The death god would be able to pull Tobi's soul wherever it would be the question relies on Minato's ability to grab Tobi for a long enough period until the death god hands reach Tobi's soul. Minato was able to land a blow in Obito, but that and grab Obito for long period of time are two completely different situations.
Death God seal is not an instant move apparently the God is rather indifferent if the technique works or not. The God wasn't pulling much hard when Sarutobi used it and Orochimaru managed to escape fairly good apart from his arms. The technique was broken in the moment Sarutobi lost grip of Orochimaru. So that leads to conclude that despite being a soul binding seal it needs a physical component that stretches for quite a while and therefore it would probably not work against Obito that would simply go intagible and escape with a minor soul/chakra loss.
The same argument would be made about other spiritual sealing techniques such as the Totsuka Sword. The sword needs to pierce and not to cut, and that is most likely because in order to seal the body must remain in contact with the blade. That's why Orochimaru's soul was able not to be completely sealed, because he severed a part of himself from the body that had been pierced, be it either the snake that fled or the Curse Marks he gave to his underlings. So we can extrapolate that Obito would be able to avoid being sealed by cutting the physical connection with the blade via intangibility.
At the end of the day Orochimaru saves Obito from being sealed by any means we know of.
Got to love Orochimaru.
