on minecraft, armor durability damage is depended on damage the armor wearer recieves.
for example player with sharp V and strength 2 potion will do more armor dura damage than player without strength 2.
so lets boost damage but only to shields, so they break slightly faster, ccnet already has countless survivability mechanics like ganks, climbing pickaxes, pearls, etc.
shields shouldn't be able to hold up to 3 people at the same time :O
10% isnt alot by the way