I think it’s pretty clear that the opal gemstone in weapons are hands down just way too strong compared to the other gemstones. It encourages you to do something you already want to do all the time - dodge - and gives a percentage of damage higher than most other gemstones, making it a no-brainer inclusion in virtually every weapon. Most other gemstones have criteria that are either very hard to consistently trigger, unreliable in their application, or have some sort of downside to turning on the bonus damage.
I would suggest first that opal only gives 7% damage. This is a big nerf, but that’s what is needed - it’s just too strong. Another possible idea for change to keep the % high, would be to change opal so you gain the damage at full stamina, so there is a cost to having the buff active - namely you need to not be dodging. Granted, this means that players have it turned on right away, but I don’t think that’s much different than currently, as 1 dodge immediately actives the buff anyway. A third possible modification could be that it’s only active in some range of stamina, say below half stamina, or above half stamina but not full stamina, so the player has to actively manage it to keep the buff active.
What is balanced and what is not balanced depends on how limited it is.
As you said - everyone has to dodge, so the existence of Opal or rather its percentage is not a problem, since everyone is able to use it following your logic. For that reason, it is balanced and I don’t see a true justification for changing it. Also, I stronlg disagree with your position regarding other gemstone. They are some better for certain weapons/builds.
no it isn’t. 400 int 600gs enchanted Opal firestaff still crits medium for 1.5k with fortify up lul. There’s enough dmg mitigation in the game rn with more coming. No thanks. Garbage take on balance. Sure nerf the opal, but buff every weapon instead.
i also use malachite on the IG, opal isnt worth cause your stamina usually regens while you’re setting up CC so you’re gonna lose damage, and keep stamina for dodging melee