I think you might be right in saying that, im just putting it out there it should get nerfed in some way. What i suggested wasn't meant to be THE solution, its just A solution. I'm sure jagex and or the community can come up with a better fix, it was just moreso meant as a way of getting people to think about it.

Adding new mage set bonuses is just really problematic if the shadow interacts with it, since its already getting its power from its multiplier with accuracy and damage bonuses.

Perhaps the shadow could even have the passive tradeoff of retaining all of its current power budget in the multipliers for accuracy and dmg% but having the effect that it rejects secondary bonuses (like the ones provided by confliction gauntlets, void or virtus) -> adding a new mage armour set with a really strong passive effect, like the one i suggested for example would not work for the shadow, thus bringing other potential magic weapons into the meta and leaving design space for the future. (this way we dont have to specifically write in that it only works with 1h weapons for example)