I've checked if I get +20 Armor after unlocked the Warp-Touched Armour and I've seen that I have low Armor. Then I've checked it on the Rank 1 CSM and he had exactly +20 Armor. While I supposed to get +20 more Armor, I got -20 less. Wtf? Edit: The problem was I have replaced Mark of Khorne with Shard of Steel which was giving +20 Armor. Well, issue has been resolved. Thanks to Krayt.