Most players have enough mastery so that their CS debuff increases a mob's damage taken by about 100%. That means you deal 200% damage to the mob. Adding 3% to that debuff with the enchant increases your damage dealt from 200% to 203%. 203/200 = 1.015, or a 1.5% damage gain. Hidden Satyr deals more than that, on average, so it's better.
В общем, вот такие дела, оказывается