A duel of back and forth rapier thrusts soon becomes too much, too similar. The best sort of action for describing in words is more distinctive, more memorable.
For example: one duellist, wounded in the leg, has to fight on while standing, perhaps half-kneeling, on a single spot; or one duellist has the rapier flicked from his hand and has to scrabble to re-gather it before his opponent can deliver the coup de grace; or one duellist traps and immobilises his opponent’s rapier under his armpit.
When I’m trying to make action interesting, I always look to see if the setting can contribute. Where does the duel take place? Perhaps there are low-hanging tree-branches—so much you could do with that. Or maybe cloaks discarded and lying on the ground—further action possibilities. Or a rising sun that might dazzle the eyes …
The more unusual the setting, the easier for the author to generate unusual developments in the action. There’s just one qualification: the setting has to be already present and in place. You can’t go suddenly discovering low-hanging tree-branches only when the action needs them. It’s a bad look!
Film directors aim to make action distinctive and memorable too, and they’ve repeated many of the most obvious bits of business so many times they’ve turned into clichés. Maybe you though that about my example of someone scrabbling to re-gather a weapon, rolling aside just as the opponent’s blow slices down? Yeah, it summons up memories of a hundred movies.
The only saving grace is ..................