If you scroll down the Pally forums you'll see a thread called "Haste is a lie". I had the same issue where even at lower levels of haste, SimC was giving me a Vers > Crit > Haste > Mastery priority. Apparently Haste unlike crit/vers fluctuates from high priority to low priority as you reach certain breakpoints. If you check your plot of Haste compared to Vers and Crit you'll notice haste fluctuates like crazy.
To make this spec playable, I would still recommend trying to get 25% haste any way you can. And then stay between 25-30 while going for vers/crit depending on what your SimC results are. Avoid mastery as usual.