"...weak enough to lose to some wannabe nine-tails jinchuriki..." I kinda disagree here.

Tobirama's fight and Darui's fight are totally different.

Tobirama group was already attacked by Kinkaku Force. That leaves the factor that he's already weakened.

To hold off 20 elite ninjas with Gin and Kin, who had power of Kage level (with 9 tail chakra) for period of time to let his group made a safe escape.

Imagine scenario where 20 ninjas splits in small groups to chase after his group and had to defend that.

Meanwhile Darui's fight he and other ninjas were able to all-in those two, thus they struggled to win with the help of Sage Tools.

I personally like him as Hokage more than others, because of his leadership skill and decisiveness, whereas Hashirama was too kind and too soft, which led it to downfall of Konoha.

If Tobirama lived long enough, I believe Konoha military strength would be as good as Kumo.