Having even a tiny bit of elemental attribute helps A LOT. If you're one to smack things around(melee), rather than blow them away with skills, then having elemental equips should definitely be considered.
I, myself, have a level 218 Champion. I'm not a pro at all because I started her back in March, but from how I still play, I still chug around my Golden Lion Shield, comp'd with Dark Attribute.
But because you're a Duelist, elemental attributes will greatly help in increasing your attack power, not only melee-wise but skill-wise as well.
Earthquake Blade: AP × (Magnification% - 60% + (Soil% × 2))
As you can see, if you have even 5% soil attribute, your Earthquake Blade will be stronger than someone who has the same stats as you, but has no soil attribute.
But, I never really got too into Duelists honestly (deleted my Duelist right after she hit 3rd), so I highly recommend you to check ggftw's wiki. They have the formulas for all your attacks and such. So you can calculate it from there~
Hope this helped even a little ;o