Shields Block 100% Damage From Weapons That Do 5 Attack Damage(melee)

Currently shields don't block attacks completely when the attack power is 5 or higher. Shouldn't a shield be able to protect a player from damage? Otherwise, why is it even called a shield when it only protects only a part of that damage? I'm suggesting that shields block 100% damage from weapons that do 5 attack damage and lower. Only then if a player gets a hit higher than 5, the shield will not be able to block 100% of that damage and will only block a part of it. I know that critical hits don't bypass shields anymore but if a player lands a critical hit with say an iron sword (that now does 6 attack damage), then that's considered more than 5 damage and shield will, as said before, only reduce some of that damage.