SimC and Affliction

[Palmz]

That does sound right since I did a plot sim aswell and the plots for haste, crit and mastery improved linearly. There was no "jump" in the dps increase at a certain point.
But it still doesn't answer the question to how the gemming and reforging should be done since none of the guides follow the stat weights as SimC does and SimC doesn't really help with how to gem correctly.
I could gem and reforge everything into haste and it would show mastery being prioritized and when I'd set those new stat weights into, say, ReforgeLite, I'd tell me I have to reforge away from all that haste I just reforged into. :/ I seem to have a hard time finding a balance.

It's a hard balance and no one is right or wrong about their reforge or gemming choices. People just need to discover what is best for them and not try to copy another player's gemming and reforge options. There are min/maxing options for every style of fight but it's just too damned expensive to keep up for most of the population. Even with 500k+ gold I don't like the idea of having to reforge and re-gem for every fight but I will for the sake of progression. You can get an idea of what Simcraft is trying to tell you but believing exactly what it tells you is your first mistake.

Stats priorities are all a mess because Intellect, Mastery and Haste can all be interchangeable between fights to mix/max your dps. As far as single target goes with low amounts of movement or no movement I like to gravitate towards Int> Hit cap > Haste 4717 > Mastery. High movement Int > Hit cap > Haste > Mastery. Add in 4-5+ mobs to a fight and Mastery begins to overtake Int and Haste BUT this is where it gets confusing. If you are moving quite a bit then Haste and Int's value start to re-take over if you can't keep up 100% uptime on every mob, but if you aren't moving very much and keeping up every dot, on every mob, then mastery is very good. Also, if you are in a fight where there aren't constant adds going out, say like in Will of the Emperor and the add phase is temporary along with more uptime to single target the boss, then mastery's value drops again. Amber'Shaper Un'sok's seemed like a good fight to gem and reforge for full mastery but I found out that with damage modifiers like in his final phase, is just doesn't keep up with Int and Haste. I might be biased towards being Hit capped, but as far as everyone's gemming and reforging ideas for Int,Haste, and Mastery...no one has the end all be all choice because we actually have three stats where one can be better than the others depending on the fight.

As for me though I like to keep a happy medium. Int is always the safe choice, along with a good balance in haste and mastery. So far that's been the 4717 haste cap and the rest going into mastery. Once I get a higher ilvl I will go for for the next haste cap as long as I don't have more haste then I do mastery. Hit capped of course as well.

[-aiko-]

I recommend playing around with different builds and simming each one. The reforgelite addon (which I used in conjunction with wowreforge.com) make it really freaking easy to reforge. The enchants you will switch out as well (haste/mastery) are usually very cheap. I was similarly confused as my stat weights also showed haste far above the others. But when I reforged, I lost DPS. In the end I basically tried 4 different builds:

1. Haste > Mastery > Hit
2. Mastery > Haste > Hit
3. Hit > Haste > Mastery
4. Hit > Mastery > Haste

Now I think it's important to note that my current ilevel is low (472) which, on top of logic, tells you how different our results will be in comparison. But here is the DPS I simmed with each build:

1. 74523 - Haste > Mastery > Hit
2. 76552 - Mastery > Haste > Hit
3. 71420 - Hit > Haste > Mastery
4. 72512 - Hit > Mastery > Haste

TLDR: Stat weights are whack. The best thing you can do is just test out different things and see what works best for your gear.
Edit: I also aimed for 4717 haste with each build. I suppose I could have also tried each build again while not trying to keep the 4717 haste, but 4 was enough for me.