Only 13% increase from 6% haste. (w/ double marches and haste)
Now if you had 19% haste, it'd be a 20% increase (which would still be a toss up but I'd have to do the math), but zerk is definitely going to give you more than a 13% increase.
The more haste you have, the higher % increase you get from adding haste. If you have 19% haste prior to earring and shield, you'd get the maximum increase from the combo. With 13, you come far short of the max increase.
19% haste and earring + shield, it'd still be a toss up w/ /war, would actually have to do the math, UNLESS you head a dnc in your pt. Then /drg should win by far.