The mirror shield (attack 0.0, defense 14.5), reward from 100th dragon dungeon, could have some extra attribute like onyx dread armor (defense 18.4, 1% magic resistance, 1% hp steal) which is reward of 100th demon dungeon . Because it will incentivate more players to do that dungeon. Some updates ago, onix dread armor didn't have any extra attribute too. And now i saw players negotiating this armor as a equipment to wearing, not just as decoration like it was before. I think mirror shield could be the same, at least used by players in low or mid levels.

+1% magic resist will be great for quest item

Agreed! Good proposal . 1-2% magic resistence seems okay

It was a big disappointment when I got it years ago.

Yes, nice suggestion to improve that item and turn it really useful in game.
I propose alternatively an anti-paralyze effect - only against monsters, not about pvp paralyze spells, if possible - for run inside respawns with many paralyzes or just to leave them faster.
Like a real "mirror" reflecting all paralyzes. Then the dungeon reward will be much more valuable.
I think that will not affect anti-paralyze potions, because this shield will be not used while players are hunting, only when running away of paralyzes.
The physical defense of this shield could be zero 0. By this way, it could be used by all class, not only warriors.
So mirror shield will never be the main shield for defense in hunts or pvp, of course without % magic defense in my proposal.
Again, containing just anti-paralyze effect, for example: (attack 0.0, defense 0.0, 100% anti-paralyze).
It should be more useful like a temporary and situational option between the player's items.
Situational because differently of anti-paralyze potions which are perishable and a complement for current equipments
,the shield needs to be equipped for provide the effect, and as a 100th dungeon reward item, it's not quite easy to obtain.
With the shield equipped, player will lose at least physical defense given by main shield/quiver/spellbook besides % magic resistance, % critical hit boost, % hp steal, magic level, melee skill or distance skill too. Clearly unusable in battles and hunting.
I consider it a fair ''exchange'' to get ''infinite'' anti-paralyze, so that will not be an op or abusive item.
Thus, anti-paralyze potions remains usually active in hunts/pvp and mirror shield could be a new choice to run away from caves or escape monsters traps. In fact not a real shield, but more similar with a utensil or a tool holding a very specific and limited use in game.
Lastly, i believe this casual mechanic of swap a part of set for another is interesting and turns the game more dynamic even in non pvp server.

This idea is very interesting! The swap part introduces a cool gameplay

Well thought out i agree with it.