This AA does not provide ANY benefit. It does not provide anything beneficial and is totally waisted AA points.
This does not appear to be fixed as of the 4/27/21 update. I am comparing before/after damage numbers (naked and no other AAs) with and without any points in this AA.
How are you testing the before/after damage numbers? Have you tried checking the damage a mob takes from your abilities?
Testing performed today and this AA is now showing a partial increase. I show an increase of 3.4% with 10 points in this AA, but AA indicates a 6% increase. Testing was done with combat mastery buff from a monk with no other AAs. All armor, buffs removed while testing. I tested multiple times to ensure the combat mastery buff returned the exact same values. This AA is still broken.
There appears to be a significant drop off in the benefit of this AA as I put my gear back on. With about 100k potency (just armor on) the increase with 10 pts in this AA went down to 1.95%. With about 340k potency with all gear, mount, familiar, merc the increase with 10 pts in this AA went down to below 1%.
I posted this in the weapon expertise thread as well: Can you private message me your character name and what server you play on please?