Enlightenment mana shield testing

Red Spider hit me for 10~18s with Rank 6 Mana Shield, 662 Int, and no armor but Royal Knight Boots and Gloves (both 4 Def, 2 Prot), a Tail Cap (1 Def), and a Wedding Ring (1 Def, 1 Prot); left me with 98 Def and 6 Prot (10% Damage Reduction). It hit me for 8~14 with Pumpkin Bat Costume (4 Def and 3 Prot from upgrades), resulting 102 Def and 9 Prot (15% Damage Reduction). It hit me for about 7~10s with Royal Knight Armor (24 Def, 15 Prot, Rank 1 Heavy Armor Mastery) for 142 Def and 31 Prot (35% Damage Reduction), and then 3~5s with Kite Shield (2 Def, Rank 1 Shield Mastery) for 165 Def and 42 Prot (42% Damage Reduction).

I didn't do enough conclusive tests since I ran out of MP so fast, but its quite clear that equipment masteries are doing something...?
No wait. 41 Defense from the equipment masteries would reduce the damage to 1; that would only leave protection.

Seems like Mana Shield only affects Defense and has no bearings on Protection?