O.o, I honestly haven't regemmed since they nerfed fury, I don't even know what the hit cap is for arms, and I knew i was way above the cap for fury. Also, keep in mind I'm a draenei, so add about 32 to that.
With Weapon mastery and SoA expertise cap on char panel is 18 expertise shown
26 is the dodge cap,
That means your char sheet will show 18 expertise skill at that point. IF you do not have Weapon mastery then you will need 18 expertise skill from gear meaning your expertise on your char panel will show 26 skill.
So in simple trust your char panel skill, if you have weapon mastery you need it at 18 to be capped if you don't have weapon mastery you need the skill to show 26
As a side note its always good to refresh everyone on this
Personally i would drop 1 points our of improved ms and put in weapon mastery, i would take the 2 points out of prot and put into improved Execute. As you get more expertise and sit at 26 expertise on the char panel then i would take the point back out of Weapon mastery and put into improved ms. And yes, i would Gem for hit and try to get a grim toll so you can then switch out of hit gems down the road