Tested the Shadow shifter artifact. For some reason the Cooldown enchantment doesn't reduce the base 10 second cooldown of the artifact.
Step to reproduce the issue:
1. Equip any type of armor with cooldown(doesn't matter what cooldown, what lvl or who much cooldown)
2. Equip Shadow Shifter and use it.
3. Hit any mob or shot arrows.
Expected result: Cooldown Enchantment reduces the Cooldown of the artifact.
The Result: Cooldown of the atifact stays the same and the enchantment doesn't work with it at all.
Also tested this with a armor piece that was modded (Cooldown Lvl 100=instant ready artifacts) and the Shadow shifter cooldown also didn't change.