I DOO!!!
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nah seriously thought Kishi was just using them to show hwo the new has surpassed the old, and that sort of thing. even though the kages are holding down the juubi, while Naruto and Sasuke double team it.
Tobirama was brought back to give a bit of closure to the Uchiha feud (or potential closure)
Hiruzen was brought back to confirm Itachi's life (redundant but whateves)
And it seems Minato was brought back to give Naruto the other half of the kyuubi chakra. They did/do still serve a purpose. But I'd rather it be a combatant one.