I noticed tempest III foes not show the 5% here.
Fighter capstone shows up... and items show up stacking. Monk windstance show up.
Please look into this... and while ya at it raise tempest III double strike a little, 5% be way too low for something items and others can attain in a heartbeat. Get your head out of the clouds - or other places - and put some value in higher level PrE tiers.