Lots of feats are available to improve how you use your weapons, including increasing the chance of landing a critical hit. Until I presented Armor Focus Feats) there weren’t many ways to improve how well you use your armor. Here I present some more feats that allow you to make better use of your armor by reducing the chance of a critical hit or sneak attack doing extra damage to you.
Armor Fortification [Armor Focus]
You gain some protection against critical hits and sneak attacks when wearing a chosen type of armor.
Prereqs: BAB +1, Armor Focus
Benefit: Choose a type of armor for which you’ve taken the Armor Focus feat. When wearing this type of armor you gain the benefit of light fortification (critical hits and sneak attacks have a 25% chance of being reduced to normal damage). You lose this benefit when denied your Dex bonus to AC.
Special: You may take this feat more than once. You must choose a different type of armor each time.
Greater Armor Fortification [Armor Focus]
You negate critical hits and sneak attacks when actively wearing a chosen type of armor.
Prereqs: BAB +16, Armor Focus, Improved Armor Focus, Greater Armor Focus, Armor Fortification, Improved Armor Fortification
Benefit: Choose a type of heavy armor for which you’ve taken the required feats. When wearing this type of armor you gain the benefit of heavy fortification (critical hits and sneak attacks are reduced to normal damage). You lose this benefit when denied your Dex bonus to AC.
Special: You may take this feat more than once. You must choose a different type of armor each time.
Improved Armor Fortification [Armor Focus]
You become less vulnerable to critical hits and sneak attacks in a chosen type of armor.
Prereqs: BAB +8, Armor Focus, Improved Armor Focus, Armor Fortification
Benefit: Choose a type of medium or heavy armor for which you’ve taken the Armor Focus, Improved Armor Focus, and Armor Fortification feats. When wearing this type of armor you gain the benefit of medium fortification (critical hits and sneak attacks have a 50% chance of being reduced to normal damage). You lose this benefit when denied your Dex bonus to AC.
Special: You may take this feat more than once. You must choose a different type of armor each time.
Notes: Moderate fortification has been reduced to 50% effectiveness in my campaign from 75%. This makes the math tidier (percentage doubles each time) and fixes what seems to me to be disproportionate gains for the ranks of fortification.