I was playing around with stats weigths a bit and I think I've found a fault.
Yoica @ Dunemaul - Mr. Robot - World of Warcraft
When you click 'Show stats' and set it to rating it says I have 1200.78 mastery in the optimized column, but it should be 1506 (not including trinket proc/use). There is 305.22 mastery missing and this exaclty what the proc/use mastery number is in the first column.
So for some reason the proc of apparatus switching from Mastery in the 1st column to haste in the optimized column is also being removed for the 'fixed on gear' mastery rating.