Really stinks this doesn't go past haste overcap (at my level it's 182%), but if you can settle with 25% haste instead of the 45% you can get from Potions of Alacrity or are trying to save money, this should be a useful macro while using it.
/timer 295
/useitem Robe of the Whistling Fists
/pause 150
/useitem Robe of the Whistling Fists