Merciless resolve skill from nightblade assasination tree bug

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Focus your senses for 40 seconds, increasing your Critical Damage and Healing by 2% with every Light or Heavy Attack, up to 5 times. While active, hitting an enemy with 5 Light or Heavy Attacks converts this ability into Assassin's Will, allowing you to fire a spectral arrow for half cost that deals 4752 Magic Damage, and heals for 50% of the damage dealt if you are within melee range.
My critial damage is 57% without merciless resolve slotted, that means with this skill turned on I should get 2% every light attack up to 67% however my critial damage goes up to 59% (it changes from 57% to 59% but doesn't go any further with following light attacks). My critial damage goes back to normal (57%) after using spectral arrow (so it works properly in this case).
It's either visual bug in advanced stats or the skill itself doesn't work properly and gives only 2% increased crital dmg.

It's exactly the same for critical healing, it's increased by 2%, doesn't go any further.