Minecraft wiki entry for Development_versions, associated text: Added armor toughness to minimize the effects of the new armor penetration mechanics.
Diamond armor and netherite armor now have a toughness value of 2 and 3 respectively.
Netherite armor will now reduce more damage than diamond armor.
Tweaked armor reduction calculation to account for toughness.
Armor protects less due to the new penetration system, armor points count for less as the attack strength increases: each 2 done by the attack reduces the effective defense points by 1 (), but not below 20% of the armor points. Each armor point now defends 0.8% to 4% instead of always 4%.
Lowered the amount of knockback resistance granted by netherite armor. Each armor piece gives 10% of knockback reduction instead of 22.5%, so a full set reduces 40% of knockback instead of 90%.