​The Patch Notes for 4.0 has been retroactively changed which makes it very confusing regarding how armour is reduced with difficulty now. What is clear is that Substantial difficulty never had any armour reduction in Patch 4.0 (by mistake), and that this was made final with Patch 4.1 to make Substantial difficulty the same as it was in Patch 3.1.

What makes things confusing is that in the past the Patch Notes for 4.0 were:

• Ruthless: Player's armour reduced by 20%.
• Substantial: Player's armour reduced by 10%

This has now been retroactively changed to:

• Ruthless: Player's armour reduced by 15%.

So did Ruthless difficulty during Patch 4.0 have a 20% or a 15% armour reduction?

What makes this even more confusing is that the Patch Notes for 4.1 says armour has been increased by 10%.

So does Ruthless difficulty in Patch 4.1 now have a 10% or a 5% armour reduction? (​Is it now effectively -20%+10%= -10% or is it -15%+10%= -5% armour?)

The Patch Notes also doesn't explicitly say anything on how armour is reduced is in Lethal difficulty.

Is it assumed that Lethal difficulty has the same armour reduction as Ruthless difficulty? Does Lethal difficulty now has a 20%, 15%, 10%, or 5% armour reduction, or is it something else?

I'm writing a guide on the difficulty levels in Operations so this information is important.

Okay so I resorted to datamining the game and answered my own questions. The armour reduction for each difficulty in Patch 4.1 is:

• Minimal: Armour is not reduced
  
• Average: Armour is reduced by 25%
• Substantial: Armour is reduced by 50% (was 50% in patch 4.0 by mistake when it was planned to be 60%)
  
• Ruthless: Armour is reduced by 55% (was 65% in Patch 4.0, and was 50% in Patch 3.1)
  
• Lethal: Armour is reduced by 75%