Jounin because of his low chakra reserves and poor stamina. If he had these on a more balanced level, I would say mid-kage level easy.
Tobi does have Senju DNA though. Kakashi has been said to have low chakra reserves but from what weve been seeing lately thats not true at all. He is at least low kage level.^ What about Tobi? Kamui is basically a space time Justu, and Tobi spams it. I wouldn't call his chakra reserves impressive.
Tobi does have Senju DNA though. Kakashi has been said to have low chakra reserves but from what weve been seeing lately thats not true at all. He is at least low kage level.