It's already implied that Hiruzen fighting capacity wasn't enough to handle a powerful threat like the Kyubi. That's why he was waiting for Minato. In fact he almost died against Kyubi's TBB if Minato didn't intervene. Seems that you underestimate the threat that Kyubi represents and especially what the masked guy represented for the future. It's THE reason Minato sacrificed himself, for the sake of the future. Without his decision of sealing the yang of Kyubi's chakra in Naruto, there would have been no ninja world right now. It's something that Minato forsaw from the start, the threat the masked guy represented. Even if he killed the Kyubi and lived, what would he have done if the masked guy came later along with 7other Bijuus to destroy the village? That's probably one of the reasons he needed to make his son a Jinchuriki, so that the strongest Bijuu, having a host could fight more efficiently against a future threat that the masked guy could represent
I agree though that thru accomplishments, Tsunade did really well to do her best to save the village, but doing his best doesn't necessarly means it was useful. Whether Tsunade saved life or not during the Pain's attack, many people still died and herself was incapable to save the village. If not Naruto, Konoha would have been completely destroyed already and everyone inside the village as well since she was already as good as dead by the end of the village range Shinra tensei. It's Naruto the one who dealt with the enemy because of Tsunade's incapacity to do so, it's Naruto the one who reconverted Nagato so that he could revive the villagers(that act making Tsunade's act of saving villagers useless btw since they got revived anyway)
Hiruzen as well didn't do much. He maybe had the longest reign, but also the worse accomplishments as a Hokage. During his reign, all the Uchiha clan got killed(Minato even said he could have probably avoid that fate), he was incapable to regulate the situation with the Hyugas. In fact, he was a bad politician, because it's really funny to see that Kumo attacks Hyuga clan by trying to kidnap a Hyuga member, but they are the one who still complains about it by wanting to have the leaders head instead because of the Hyuga clan defended themselves against a traitor. How is that possible? What did he really accomplish that was good beside only giving someone as weird as Danzo full power?
