In my opinion, Mist Elves should have a way to protect themselves from Iron, but it shouldn't be trivial to obtain.
At the very minimum, I'd make it so that the Elemental Gauntlets protect from wielded iron items - that is, things in the hands. Perhaps the same could apply to Thick Gauntlets.
Having all gauntlets and gloves protect them from iron weapons and shields perfectly seems like it defeats the primary point of the danger.
Alternatively, make it so that iron artifact items are like iron rings - you can only wear/wield one such item, but one is safe. I'd use the same counter, too - so you can't wear both an iron ring and an iron artifact at the same time, without the negative effects.