Previous posts here:
After a lot of digging on EJ, I found good evidence for the haste regeneration formula, and it roughly corresponds to my somewhat loose testing so it seems to make sense. The haste energy regeneration formula is as follows:
energy regeneration/second = 10*(1+ haste%)
In other words, if you have 20% haste, you regenerate 12 energy/second. If that sounds underwhelming...you're probably right. At 20% haste, in order to gain one extra shred you wait 20 seconds. That's helpful, don't get me wrong, but with the sorry state of damage on shreds this isn't nearly as impressive as you might think.
Furthermore, the relative percentages of damage aren't close to what they are now. With the loss of arpen and the loss of Feral AP, melee damage is significantly less. Ironically bleeds are significantly more than they were before (or perhaps they're the same, but as a relative level they went higher. I'm seeing reports of bleed damage being as high as 50-60% of overall damage at raid-buffed levels, and melee close to 25-30%.
With melee that low and with bleeds that high, haste only improves about 50% of your total damage. If you assume that shreds are 20% of your damage (which is actually a bit high) and melee is 30%, each percent of haste does the following:
1% haste increases your melee damage by 1%, which increases your overall dps by .3%.
Assume the rate of shreds per a fight is roughly constant. In a 40 second period I showed that you have about time to do 7 shreds. This means that each % of haste in a 40 second period gives you .1 shred, such that 10% haste gives you one extra shred in that time. This equates to 1/70 more shred damage per 1% haste, or:
1% haste = 1/70 * 20% = .28%
The total gain of dps for haste is thus about .6% directly. In addition more haste gives you more combo points, which is potentially a source of ferocious bites - but only a small one. You'll get haste%/70*crit rate more combo points per % of haste in a 40 second period, which at 50% crit rate is about .07 CP per haste%. Not thrilling.
Sadly, this is about as good as I'm going to get without a simulator, but it roughly confirms reports from others about how well haste scaling and haste conversion is compared to other stats. This disappoints me; I want haste to be an awesome ability because haste is fun. Being able to do more things is more fun. Hitting harder, bleeds doing more, critting more often - these don't directly impact the rotation and ability to do actions like haste does. Sadly, haste doesn't look to be that great.
Note that if haste made dots scale, haste would immediately be competitive with crit rate and likely close to agility. Which...is what blizzard wants, right? Sigh.