The Elemental Wheel

[KikoriL]

Resistances are more relevant right now than people think. Someone tested it pretty well and found resistance stacking has a sizable effect on successfully protecting someone from a confirmed elemental attack.
The issues, though, are obvious. Needing a gearset for each element isn't efficient. It's generally safer after a while to just burn stuff down. Attacks with enough damage WORTH mitigating generally appear unaspected, unless you're just REALLY into pony farming with some terrible luck on your side to justify resisting those high damage blows. And it can still get expensive to max out resistances in crafted armor.
I'd imagine piling on resistances goes hand in hand with piling on VIT melded accessories in new content. Useful for learning, shaved off bit by bit once it's figured out, removed to the minimum (zero, in resistances' case) once it's mastered.

[whiskeybravo]

And it can still get expensive to max out resistances in crafted armor.

Not to mention the limiting factory of inventory space. If you have most classes leveled then you're armory chest is half full with regular or best gear, then you'd have to add all different elemental gear sets. Costly, space consuming, of little benefit (at this point at least).

I do agree with the OP tho, elemental advantages are key in most single-player FF games. It wouldn't be impossible to implement in this game, but instead of relying on melded gear (due to inventory space concerns), I'd rather see something like enflame, enthunder, etc kind of damage buffs. Abilities that each class has vs loaded inventory. Could even make them cross class skills so you could equip them for just a single battle and then swap for the next.