Maybe I am also relying on the Knight's shield a lot, which would otherwise get the swordsmaster dead.
That would definitely do it, IMO swordsmasters depend fairly heavily on one-shoting anything they go up against with huge combos before it ever has a chance to actually hit them; one of the reason's I've had better luck with a pure +AGI swordsmaster build than a half and half one.
Just managed to beat the Dark Lord for the first time on my very first hunter run, in large part due to that amazing wolf-healer girl who let me get by with a fairly light weapon and still smash all the walls and chests that needed to be smashed.
I ended up using one of her own friend tablets on here after she transformed, not sure if you can keep her any other way.
Surprisingly I actually started to wittle away at the demon lord's hp starting about the 4th time he showed up with my bow, though I broke my bow shortly afterwards and eventually just resorted to a lucky flaming axe I found along the way. Sadly forgot to take a screenshot on winning, so here is one of the end of the replay (Ending ranks were: Level - C, Distance - S, Battle Grade - A, Treasure - S).
I do wish that quivers/shields were in a different slot from rings and other accessories though. It seems strange that I have to take my rings/necklaces off in order to put on a shield or a quiver. (Also I found that if you smash down the wall into the dark brotherhood's house instead of actually getting in through the door they all just stand there staring at you, it's kinda creepy.
)