But Zoro as a fighter is relevant, he took Luffy's pain and didn't want to let Sanji do it in his place, he literally was sacrificing his life to stop "Hakkai" and save everyone in the Rooftop. These actions tells a lot.
Nami's role is run around with Usopp hitting some fodder, and getting saved by Sanji
Meanwhile Sanji and Zoro are called the wings of Luffy, and the "stars" by Whitebeard's 1st Division Commander.
How the heck Nami has more "Main character" traits than Sanji?