As everybody noticed aside from crit exp and hit, haste and mastery are kind of useless for Arms spec. Recently I came up with an idea how to improve either haste or mastery value which would improve scaling and gearing. This would come as a new passive ability (dont know the name yet):
After 3(maybe more) normal or opportunistic strike hits your next special attack deals X%(not much) more dmg.
Now the idea is that stacking haste would speed up the ramp up process while stacking mastery would be a possible choice too. in addition to that hero/bloodlust would provide a significant boost to dps aside from more heroic strikes.
as for pvp this would be like 4-5 sec stacking buff so you can los warrior and those stacks will disappear. Besides in pvp you dont have that much haste or mastery.
thats my thought. constructive feedback or improvements are welcome.