Something about the Uzumaki Clan not showing themselves during those times tells me that more than a Shinobi Clan, they were kind of a Religion. Or rather, a Noble Family, dedicated to provide spiritual guiding. Think about it, why else would their sealing techniques be so powerful that the actual Grim Reaper could be summoned by them? Something makes me thing that, while the Senju and the Uchiha were fighting each other, the Uzumaki's enemies were something else... Spirits, or powerful creatures. Who knows? Maybe the Juubi's splitting into nine Bijuu left more in that world than just nine Bijuu! Why specializing in just sealing techniques? What were they trying to seal, to contain or to stop?
There is something here. Mito's timing at sealing the Kyuubi was too great, and for one, she looks like the proper priestess, doesn't she? Ain't priestess in japan looked like spiritual guides? Derp Obito, what cha thinking?