(this post is exclusively about BM)
As always, getting too much of any one secondary stat can be bad. As an example, the more haste you get, the more valuable crit and mastery become per point, eventually passing haste in value. Personally I prioritize haste on reforges, and leave TED unreforged (full mastery) as a quick way to balance the stats.
Depending on the fight length, the value of mastery can shift drastically. If a fight lasts exactly 6 minutes and 40 seconds (worst case scenario), it means you were only able to cast two stampedes, and it came off cd right as the boss died. Seeing how stampede is 8m~ damage per cast when stacked with dextrous and it the strongest modifier it has is mastery, it's a big deal.
For individual fight rankings/progression, if you know exactly how long a boss encounter will last, you can fine tune your mastery to haste balance. As an example, I went mastery>>haste>crit for heroic garrosh progression because of the way the fight works. It always goes 2minutes on boss -> 1 minute transition (some boss uptime) -> 2 minutes on boss, etc. Because of this, you will have higher % stampede uptime on the boss as compared to a patchwerk fight, and boss damage is king for this particular boss. If you're fighting a boss that will give you low % stampede uptime, haste is > mastery.
A lot of fights this tier have burst aoe phases (immerseus, sha of pride, galakras, shamans, malkorok if you hit adds, spoils, thok, siegecrafter if you do mines, garrosh). For burst aoe, haste has a very low value, and mastery has an insanely high value.
Also, I don't know why people are saying having low crit gives you low burst, it's quite the opposite actually. Because with full agi procs on pull you gain 35%~ crit, mastery and haste's values skyrocket for that short time, especially when stampede is used (this is the main reason haste and mastery shine with a lot of gear).
TL;DR: haste is not > mastery in all situations. Mastery=Haste>crit for high gear levels, with mastery being better for specific fight lengths. Mastery also dominates on burst aoe (8-9 of the 14 bosses). Haste is only better than mastery for pure single target fights with unknown lengths, or lengths that make stampede uptime low. Mastery actually beats haste more often than haste beats mastery, but again, there is a balance that must be found so one does not pass the other in value.