Reminds me of the time I wanted to write a quarterstaff fight, so I went back to that most classic of quarterstaff fights--Howard Pyle's The Adventures of Robin Hood. Took me over 10 minutes to find it. It was ONE SENTENCE long, but with the build-up, that one sentence captured an entire imagination.
I've honestly never waded through past Fellowship, however you've got me wondering if Tolkien actually wrote the beheadings or just put the right words down so you could imagine that's what happened.
Well, for instance, the death of Boromir is never depicted in book. We see only its aftermath, his confession to Aragorn, and Pippen's recollection to Denethor. And yet his valiant, desperate attempt to redeem himself for his failure with Frodo was a vital part of the film, I believe -- and in all honesty, I never had much connection or sympathy for the Boromir character before I saw Sean Bean's interpretation of the role.
So maybe it can go both ways. On paper, the battle doesn't necessarily have to be drawn out at all. We know how these things go. But on film, the choreography is the thing, and it all has to look amazing.
As far as Gimli goes? When they encounter the riders of Rohan, Gimli tells them he's more interested in hewing orc necks than scalping men's heads. And at Helm's Deep he complains that his axe was notched because of an orc wearing an iron collar.