I know Hiruzen is, i've only being saying it for the last 20 flipping years lol. But i'm focusing specifically on Old Man Hiruzen, not Prime. He has been noted as being 'poor' compared to his prime by Emna. I'll kind of fully answer this in my reply below.
Do team Orochimaru even have any sealing feats? If not, they lose everytime. That's pretty much it really.
Ok, firstly, Tobirama has no feats and relatively little hype. I just don't see how we can accurately measure his strength. All we have is his Edo variation as seen against Hiruzen. We don't know how his S/T worked. We know nothing really. That's all. Power scaling is irrelevant, because everything is relative. It only shows that, whilst the Senju brothers would seem stronger, so would Hiruzen. It doesn't necessarily follow that they would whip out stronger moves etc, although I understand what you're saying.
Hashirama being Edo makes little difference, due to the fact he already had the no hand seal regeneration ability from when he was alive. So he'd be pretty much the same as when Madara fought him. Being Edo, and having EMS, Mokuton and the Rinnegan just makes him superior to Hashirama. Orochimaru can be dealt with the 25 Susanoo clones. As i've already stated, Banshou Tenin + Human Path combo is pretty much gg for anyone, as we know even KM Naruto was unable to react when under the influence of Banshou Tenin (only his chakra arm saved him). Perhaps only Tobirama could avoid this with his S/T, but as I stated, we know nothing of how it works or what he requires in order to use it.