A known change going into BFA is that
正义盾击 will increase your armor as a % of your Strength stat. This orients
正义盾击 to be strong against physical damage while losing any value vs. Magic attacks. This change is fine. I'm ok with this change.
A lesser known change is how armor interacts with Block. Currently on alpha, the amount of damage you block reduces as you get more armor. For example, on my 117
圣骑士 in Alpha quest gear, I have 33% baseline block DR. When I hit
正义盾击, it drops to 14% DR.
Now if you consider
神圣之盾, a Protection Paladin talent, I gain the ability to roll a block on magic attacks. This has been a tool since WOD for Paladins to counter consistent magic bosses like
克洛苏斯. With the changes to
正义盾击,
神圣之盾 will be the only way to reduce magic damage for Protection Paladins in BFA.
However, when you put both changes together, pressing 正义盾击 reduces the amount of magic damage I could reduce via 神圣之盾. In a fight like 克洛苏斯, it would be better to spec and sit on 正义盾击 charges (or use macros to cancel the aura) than spend them and take more damage.This is problematic and counter-intuitive. Pressing an active mitigation button shouldn't cause me to take more damage than I would have if I didn't press that button. No other tank has to deal with an interaction like this. It will lead to /cancelaura macros where am I pressing
正义盾击 for damage then canceling it right away to maximize the damage reduction from
神圣之盾. Imagine having to do
克洛苏斯 but having to /cancelaura
正义盾击 constantly as to not take more damage than we should be and maximizing damage/threat.
There will be points during Mythic bosses where, I'll be thinking, "Here comes the magic hit, let me click off my
正义盾击 so I can increase my damage reduction vs magic." Tanking shouldn't work that way.
/cancelaura macros for Active Mitigation Buffs against spell damage is not good gameplay and changes should made to avoid this situation. 