I realize some threads can be long and we don't expect folks to read every post on every page before posting, however we do expect you to at least read the current discussion posts. On the very same page you posted your question there is discussion on why the sim says haste over mastery, but why mastery is really better. Please read the current discussion before posting a question.
I'd be interested to know as to which simulation tool you used and with which gear set to get the result that mastery was "beating haste hands down". Using simc with gear varying from T11hc to T12 BiS and prioritizing mastery over haste both in terms of reforging and itemization, haste always comes out with a highest stat weight; indeed, the highest output possible listed on the simc website (Simulationcraft Results) is prioritizing haste, with swapping haste for mastery always being a DPS loss.
If a tool that is considered one of the most accurate forms of simulation is suggesting haste is better at a gear level vaguely relevant to current raiding, wouldn't it perhaps be worth mentioning it? Indeed - a quick check on female dwarf lists haste as being better in BiS. What gives?