Damage Reduction Not Additive - Sanctum Sanctorum Rank 1 & Professor X (Classic) Xavier Protocols

Kojubat

I have a single cover of Professor X (Classic) Xavier Protocols, which includes the following:

"(PASSIVE) Professor X has a comprehensive file on your weaknesses. Xavier takes 12% less damage for each active X-Men member on his team and 5% less for each other active ally."

I equipped him with a Rank 2 Sanctum Sanctorum leveled to 100/100. The Rank 1 Perk reads:

"The supported character takes 13% less damage from enemy matches."

Wanting to see the synergy in action, I tossed him in The Big Enchilada with Captain Marvel and Devil Dinosaur (to minimize color overlap and avoid other X-Men). However, the interaction did not function as expected.

Xavier Protocols should have reduced damage by 22% (12% for Charles, 5% each for his friends) from all sources.

My expectation was that any match damage should have been reduced by one of the following:

1. 35% (add all percentages, 22%+13%) [Maximum reduction from matches: 99%]
2. 32.14% (apply 22%, then apply 13%, or vice versa) [Maximum reduction from matches: 81%]

However, the following are the results of different damage sources:

Mindless One attack tile strength: 202

Damage applied to Professor X: 158 (22% of 202 is 157.56)

Expected 22%, got 22% after rounding.

Magneto matches three yellow tiles: 120

Damage applied to Professor X: 94 (22% of 120 is 93.6)

Expected either 78 (option 1) or 81 (option 2), but no additional reduction of match damage occurred.

I ran some additional tests pairing Professor X with two other X-Men. That increases the base reduction from Xavier Protocols to 36%, and would change the expected match reduction to either 49% or 44.32%.

Mindless One Eye Beam: 1732 AoE

Damage applied to Professor X: 1108 (36% of 1732 is 1108.48)

Expected 36%, got 36% after rounding.

Iron Man matches three blue tiles: 105

Damage applied to Professor X: 67 (36% of 105 is 67.2)

Expected either 54 (option 1) or 58 (option 2), but no additional reduction of match damage occurred.

I suspect this also applies to other characters with damage reduction powers, such as Rogue or Colossus. The nature of Supports is such that it cannot be moved around easily, so testing would require extra time.

<TL;DR> Sanctum Sanctorum Rank 1 Perk does nothing when attached to a 5* Professor X with a black cover.