[Rumil]

One thing to consider is that Legolas is pimarily an archer.

Admittedly he does get his 'long knife' out when needed but most of the time he is shooting from a distance. I guess Gimli and Legolas therefore have about equal chances to stop an arrow but Gimli is more likely to be wounded in hand-to-hand combat, simply because he does more of it. Add to that the orcs' lack of marksmanship and I think its not surprising that Gimli is the only one of the pair to be wounded.