Just in: As per confirmation from the players on PTR, Blizzard secretly nerfed all conversion values of secondary stats namely: Mastery, Crit, Versatility and Haste. According to them, Blizzard didn't announce any changes on the PTR today and thus, it came as a surprise after players noticed a significant change in their overall DPS.
World of Warcraft PTR Update: Secondary Stats Nerfed
Today, the PTR was rocked once again with players asking for answers from Blizzard regarding the conversion rate of secondary stats which was seemingly nerfed secretly by Blizzard. According to those that have been keeping on track, despite the increased stat value from gears due to the changes on the PTR, the resulting conversion was still lower than the current live version of the game. To get a clearer picture, here's the exact stat changes submitted by Ryumaru.
8636 Mastery = 40.84%
5145 Crit = 29.7%
255 Versatility = 0.64%
4296 Haste = 13.22%
9023 Mastery = 38.2%
5265 Crit = 23.16%
255 Versatility = 0.54%
4391 Haste = 12%
These values are taken from the same gear and thus, it's pretty clear that secondary stats are receiving a nerf from its overall conversion rate. Also, this includes the 5% baseline Crit nerf on most melee classes (in this case, WW Monk). At the time of this writing, Blizzard has yet to announce the exact secondary stat adjustments and the reasoning behind the change.
The Implication about the Secondary Stat Nerf
A player suggests that the change is somehow advantageous in the sense that it makes the secondary stats more valuable in the future which consequently will result in a more diversified yet specifically tailored gears and sets. Furthermore, it implies that players should now be focusing in optimizing their characters based on the specific stat requirements of their build rather than gaining more values from undesired or unnecessary stats. In short, one must now be keen in knowing the right choice of secondary stat to optimize their character and focus more on that stat rather than taking mediocre values from unnecessary ones.