Yes and no.
Dark is a quite âneutralâ element where no mobs have resistance to it but no mobs have vulnerability to it either (the only mob iâve seen in the whole game weak to darkness was that grey flying frog in barha forest).
With hex, the equipment you have that give dark attack will increase their dark atk by 30%. So if you have 3 headgears with 30 dark attack each, youâll get 90 * 1.30 = 117 extra dark attack.
However, if you get 3 headgears with holy elemental atk, you will deal double holy damage on mobs weak to holy (which most mobs in the game are), so that means your 90 holy atk will become 180 holy atk on those mobs. And there are no mobs resistant to holy so there wouldnât be a drawback.
I canât tell you what would be better, as that would take more complicated considerations into account (whatâs better? 30% more dmg on every mob of game, or 100% more damage on some mobs of game?).
Overall, the idea is to stack as much elemental atk as you can get, regardless of what element it is. If you can get your hands on a +25 fire atk and +25 ice atk headgear, that might be slightly better than a +30 dark atk headgear.
Comparing just 30 fire atk to 30 dark atk, dark would be slightly better overall, but worse against mobs weak to fire.
If you donât want to go crazy, donât bother too much as to what element it is in the headgear, just the value it gives.