1. She knew that Sasuke had fought with Naruto and that things were getting tense. She knew that Orochimaru had his eye on Sasuke. Still she left Sasuke unattended and to make up for that she let 5 GENIN go after him!!!
2. Hiruzen, the man that fought Hashirama, Tobirama, and Orochimaru. Yeah he could do a lot better
1 - Like i said, he left on his own, she can't predict the future. She didn't send 5 genin because she wanted to. She sent 5 genin because the village was severely weakened after Orochimaru's invasion and no more jonin were availuable (manga fact). Why not blame Hiruzen too for not being able to erase the threat by himself then? Its not just the Hokage's job to defend the village you know.
2 -
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is Hashirama's true might and
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is the edo Hashirama that Hiruzen fought against.
Tobirama's arsenal includes FTG, ET (w/ a suicide jutsu), Shadow Clones, Sensing... Yet, the only thing he used were two average Suiton jutsus and Orochimaru only contributed with a little kenjutsu.
According to Tobirama, they weren't revived
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, so no, he didn't fought 100% Hashirama + Tobirama.
Back to the point, he can't touch Deva Path, prevent Preta Path from absorbing his elemental jutsus and
more importantly, protect the villagers lives like Tsunade did with Katsuyu.
At least he doesn't have a way that we know of.