not really we are not sure of what really happened or who exactly were the other 15 shinobis or if it was them for sure who finished him, all we should understand from this is that the circumstances were all against him (for tobirama and the entire team that had a young hiruzen and danzo on it to try to escape) so this should tell you that the situation was beyond tough. you are really underrating tobirama, he was the second HOKAGE, brother of hashirama and master of hiruzen, user of s/t and creator of edo tensei, sorry but the likes of tobirama CAN'T be fodder even if they wanted too ....... U_U tobirama was a BEAST, top class