In the case of Sekiro, it's very clear-cut: he's a shinobi who's trained in swordfighting and martial arts, so it makes sense that, even though he's not at his prime at the beginning of the game, he's very agile and knows how to fight.

The explanation for Bloodborne's PC being a competent fighter could be that since it's "just a dream"™, they can fight perfectly well. Gehrman and the Moon Presence have no use for a hunter that's incapable of hunting.

But in the case of DeS, DS, and ER? I've got no explanations. Especially in the case of DS, you're on the brink of hollowing - you shouldn't be capable to do anything, really, right?

Maybe I missed something, but I can't answer that question. Thoughts?