OKay I am here now.
The reason being - people misunderstand - haste itself has nothing to do with the mastery procs itself.
The ONLY reason why haste DOES affect mg procs is the MG bug by itself:
MG that procs of MG is done INSTANTLY, at the same time.
But, on the server side, nothing can be done instantly, every thing takes time.
If, for whatever reason, server is trying to calculate the 9 procs at the same time from one attack for too long, it will be interrupted when next attack should be calculated.
This brings us to TWO things:
1 - an easily observed one - server load (server delays, lags etc) WILL greatly reduce the amount of mg procs.
For that sole reason my dps on dummy can be anywhere from 18 to 28k. There is no luck involved at 2kk+ damage done.
2 - harder to observe - haste in SOME amounts (impossible to really say for sure in what amount for every specific situation) will CHOP off some of the procs. It is hard to explain, but think of it as matching two rulers (measurement tools) with different scales.
If you know how much more measures of one scale you need to add to match one (or any other specific amount) more measures on other scale, you can find amounts when they will match perfectly, and none will be lost. But, if you don't match them perfectly, some amount will be lost, unmatched. This is what happens to haste. Big amounts of haste (yet to determine minimum amount that benefits) will obviously raise the dps. But small amounts of haste within those big amounts will not. Think of it as caps, that depend largerly on unreliable things like server load.
And this is the conclusion. UNLESS the haste you just took gives you OBVIOUS (on recount or the like) benefit to dps all that haste is a waste of stats.
I reforge haste i cannot reforge into mastery, into hit. On my current gear, it is about 450 in stat points. If I reforge that hit back into haste, I will still be over hit cap. But my dps WILL suffer.
When I said that haste is bad, I never meant to say that it is bad because it always hinders procs or whatever. I think it is bad because it bring more uncertainty into an already strange build. Unlike hit. Hit is obvious and plane. That is why I take it instead. I never said you can't overdps me taking haste instead of hit or taking haste/mastery gear instead of crit/hit/mastery. It is just there is noone yet to prove it.
And please, people. I do not like writing guides but I don't mind giving advice or sharing knowledge.
So please do not think I feel obliged to prove any point I make. I may be wrong somewhere, but I will consider myself to be right even without any foundation until I am proven wrong.
Thanks for reading this wall of text.