That might be why it doesn’t work then, because I only tested crit heals. Since you are receiving a heal, that might be why it reduced that. I should test damage but in terms of healing, here’s a combat log where showing the less damage on my heals. I should have gone a bit more in depth, it was late my bad
Combat log
11:28:01:859 [Combat] Semz took -11406 damage from Semz (Critical) <— With -1% crit shoulders
11:29:09:185 [Combat] Semz took -7455 damage from Semz
11:29:12:362 [Combat] Semz took -7455 damage from Semz
11:29:15:541 [Combat] Semz took -7455 damage from Semz
11:29:18:719 [Combat] Semz took -7455 damage from Semz
11:29:21:919 [Combat] Semz took -7455 damage from Semz
11:29:25:097 [Combat] Semz took -7455 damage from Semz
11:29:28:264 [Combat] Semz took -7455 damage from Semz
11:29:31:486 [Combat] Semz took -7455 damage from Semz
11:29:34:664 [Combat] Semz took -7455 damage from Semz
11:29:37:819 [Combat] Semz took -7455 damage from Semz
11:29:41:008 [Combat] Semz took -7455 damage from Semz
11:29:44:219 [Combat] Semz took -7455 damage from Semz
11:29:47:386 [Combat] Semz took -7455 damage from Semz
11:29:50:614 [Combat] Semz took -7455 damage from Semz
11:29:53:775 [Combat] Semz took -7455 damage from Semz
11:30:24:321 [Combat] Semz took -6929 damage from Semz
11:30:27:487 [Combat] Semz took -7455 damage from Semz
11:30:30:654 [Combat] Semz took -11555 damage from Semz (Critical) <— without -1% crit shoulders
This means that if the tank has full -1% crit armor they are getting quite a bit less healing.