the reason we have lingo for anticipation/setup and reaction/recovery is because they should always top your list as keyframes. they are absolutely necessary for what we like to call locomotion - the body simply can't move in the way you're describing. it doesn't matter that the weapon is light - the body doesn't
ever skip steps - it merely learns to do them faster.
the point of a keyframe is so that you work between them, not straight through linearly as you're trying to do. you started on the right path with keying the attack frames but then you gave up.
this sample is not my finest work - i went straight through without ever watching it so there are definitely things i would tweak. However, it is *only* the keyframes that I would use in this animation - I haven't even started to tween them! in a combo, recovery from one move is the anticipation of the next, so counting "idle" it's an 8-key animation to me : idle -- set1 -- attack 1 -- rec1/set2 -- attack2 -- rec2/set3 -- attack3 -- rec3 -- idle
How did i work? i eyeballed your major attack frames and idle for the main framing. then I added the necessary frames in the middle. I also left a little extra on the final attack, which i felt could get some more "woah!" time after he strikes since it's a finishing move. 4 is now expanded to 8 and give us a muuuuuch better sense of how to do things.
even from here, you probably shouldn't work linearly one frame at a time. now that you have your 8 keys, i would actually continue by division - finding midpoints between them. these are kinda like "mini-keys" because they no longer define proper positions, but they do help clarify the movement. Also, it's always easier to find a midpoint of an animation than it is to find the first tween of 3.