Ideas and suggestions.

Banning the King's Shield will significantly change the game, and it's unclear in what direction. Personally, I think it will make the game more interesting. But this isn't a bug fix; it's a change to the game. You could hold tournaments with a King's Shield ban, which has already been done, but not ban it completely. In principle, there's a middle ground: make it a combination of two relics: a cloak and a King's Shield of level 1 or 2, for example.