The haste plateaus are listed for general reference and knowledge. However, there are many people that I trust with my shadow priest life that say that reaching the 2149 plateau with DI creates a substantial increase in DPS.
Taken from Kilee's shadow priest guide found on MMO/Shadowpriest.com/Howtopriest.com
You need to reach a haste threshold of 2149 with Dark Intent or 2588 without Dark Intent. Reaching these points is a substantial increase in DPS, and you should try to plan a gearset that will allow you to reach these at the very least.
I'm going to be honest, the past few weeks before 4.2 dropped, I was slowly losing interest in the game and researching stuff about the class, but now that I'm getting back into it, I'm finding out these things. I don't have a lock in my raid so I would have to reach 2588 haste to hit the extra tick. After finding this out, I switched out Lavawalker for the +50 haste enchant to reach it.
Ok, haste plateaus to use that term. If you are 100 haste away from a plateau would you reforge out of hit for it..or would you regem out of int to hit it?
Depends how much hit you have already before reforging out of it. I'd try to stay around 13-15%ish (Not carved in stone, just throwing out numbers) if you're okay with being under cap and reaching the plateau. It all comes with gear, so I'm not about to tell the general public that reaching that plateau is a must cuz some people simply don't have access to the gear.