People keep asking, grr.. Since I've taken the time and money to make my own site with lots of hunters stuff, I naturally made a post about the haste plateaus. I'll keep it short here.
Note: If you mainly use Aimed Shot to focus dump, ignore haste plateaus. This play style doesn't prioritize using Chimera Shot on cooldown, thus you don't really need to be at a certain plateau. You want to stack as much haste as you can.
Marksmanship Plateau without the Chimera Glyph
Plateau 1: 4 SS, 2 AS and 1 CS in 10 seconds - 0 haste rating needed, only Imp. SS.
Plateau 2: 4 SS, 3 AS and 1 CS in 10 seconds - 299 haste rating, 5.40% haste with 3/3 pathing.
Plateau 3: 5 SS, 2 AS and 1 CS in 10 seconds - 1235 haste rating, 12.93% haste with 3/3 pathing.
Plateau 4: 5 SS, 3 AS and 1 CS in 10 seconds - 3575 haste rating, 31.75% haste with 3/3 pathing.
Recommendation: Go for the 3rd Plateau.
Marksmanship Plateau with the Chimera Glyph
Plateau 1: 4 SS, 2 AS and 1 CS in 9 seconds - 299 haste rating, 5.40% haste with 3/3 pathing
Plateau 2: 4 SS, 3 AS and 1 CS in 9 seconds - 2920 haste rating, 26.48% haste with 3/3 pathing.
Plateau 3: 5 SS, 2 AS and 1 CS in 9 seconds - 3575 haste rating, 31.75% haste with 3/3 pathing.
Plateau 4: 5 SS, 3 AS and 1 CS in 9 seconds - 6851 haste rating, 58.10% haste with 3/3 pathing.
"Plateau 5": 5 SS, 1 AS and 1 CS in 9 seconds - 1235 haste rating, 12.93% haste with 3/3 pathing.
Recommendation: The "5th" plateau will make you focus capped, but it's the only realistic one with T12 gear, unless you somehow manage to get your haste to 299, which is doubtful. There isn't any "good" plateaus for the Chimera Shot glyph with current tier gear. We might be able to get to the 2nd Plateau in T13. Bottom line, if you use more than 2 GCDs per cycle on Arcane Shot, Kill Shot, Instant Aimed Shot or similar, you will end up having to either wait for, or delay Chimera Shot.
You can of course go for the 1st Plateau and just wait for the Chimera cooldown with a bit higher haste level, but is it really worth it?
Survival Haste Plateaus
Plateau 1: 3 CS and 1 ES in 6 seconds - 758 haste rating, 9.09% haste with 3/3 pathing
Plateau 2: 4 CS and 1 ES in 6 seconds - 5278 haste rating, 45.45% haste with 3/3 pathing.
"Plateau 3": 4 CS and 1 ES in 7 seconds - 2264 haste rating, 21.21% haste with 3/3 pathing.
Recommendation: Go for the 758 plateau. There is a "3rd" plateau, you basically do the same dmg with 4 CS and 1 ES in 7 seconds as 3 CS and 1 ES in 6 seconds. You do of course get more auto shots, but the loss in crit to reach this haste level isn't really worth it.
Beast Mastery Haste Plateaus
Plateau 1: 3 CS, 1 AS and 1 KC in 7 seconds - 0 haste rating needed, already there.
Plateau 2: 3 CS, 1 AS and 1 KC in 6 seconds - 1937 haste rating, 18.58% haste with 3/3 pathing.
Recommendation: The 2nd plateau is easily reachable with T12 gear, specially if it's 391 ilvl. If you can get there with your current gear, go for it, even if you have to sacrifice crit.
That sums it up for the haste plateaus, which has been updated to NOT reflect T11 4cp, and is only for T12. It is also what you want for T13 as long as the cast times aren't changing, and of course you'll be able to MAYBE hit the next plateaus, depending on how much haste you can get from T13 gear.
If I've messed up somewhere, let me know.
You can click my signature for the whole thing.