Orochimaru is quite durable, going by the fact how he was clawed a couple of times by 4-tails Naruto and managed to cobble himself back together. So I am not even remotely buying this 'one hit from Tobirama wrecks him' - it's not feasible or a viable debating option given what we have seen. Then we have Eight Branch Technique as well, and powerful Snake summons to protect him just as Sasuke did so against Deidara's homing Clay bomb. Orochimaru also has Futon-Release, with his he deflected the Kunais back in part one, it should be effective in CqC combat or at close range.
Ororchimaru takes this mid-difference.