This is not a change in game mechanics. All tests done so far on both the PTR and Live have shown the same behavior. However, it appears some very old enchants do benefit from haste, which is probably why that behavior was accepted as common knowledge.
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I took a large quantity of data on the 2.2 PTR against blasted lands mobs -- approximately 150,000 swings -- and it appears that while Flurried (25% haste) the proc chance for various events drops.
I tested three different procs, with three different weapon sets, with both 0/5 Flurry and 5/5 Flurry in most cases.
Procs Tested:
5/5 Unbridled Wrath
[Mark of Conquest]
[Darkmoon Card: Heroism].
Weapons Tested:
MH:
[Protector's Sword]
OH:
[Protector's Sword]
2x
[Ced's Carver]
2x
[Blade of Unquenched Thirst]
Various people were beating on my mobs with the occasional kidney shot, etc. Also, the level of the mob varied. Neither of these should affect proc rates.
Analysis:
I parsed the logs by tracking how many weapon swings and procs occurred inside and outside of "You gain Flurry" and "Flurry fades from you" messages. I realize that the combat log positioning of the haste gain/loss events isn't perfectly accurate, but it's the simplest way to separate hasted from unhasted swings. I then calculated PPM rates assuming the proc chance was based on unhasted weapon speed:
Calculated PPM = proc chance for an individual swing * unhasted weapon swings per minute
As you can see in the graphs, this calculated PPM rate drops while hasted, implying that the proc chance drops while hasted.
Looking further at my data, the real PPM (total procs / time in combat) was nearly equal for both hasted and unhasted tests. This suggests haste effects will not get you more procs for items which use a PPM mechanic.
Thread Summary:
Warriors see decreased proc chances for Unbridled Wrath when flurried on both the PTR (post 1) and Live (
post 78).
Rogues do not see increased uptime on an unspecified proc buff while using Slice and Dice on the PTR - Tyran,
post 33. Short testing though - only 15 minutes per run.
Rogues see an unchanged proc chance on Fiery Weapon while using Slice and Dice on Live - Baldycenarius,
post 37
The behavior for Shaman with Flurry and Mongoose is the same on Live and the PTR - Lujaar,
post 42
Hunters see a reduced proc chance on Live for
[Don Santos' Famous Hunting Rifle] when using a quiver and Improved Aspect of the Hawk procs - Kaber,
post 72
Warriors see an unchanged proc chance on Lifestealing when flurried on the PTR (
post 113)
Instants use unhasted weapon speed to determine proc chance - Sarlunas,
post 120
Thread Summary Summary:
Fiery Weapon (tested on Live), Lifestealing, and Crusader (tested on the PTR) all see unchanged proc chances when hasted - i.e., they benefit from haste. All other procs tested so far on either Live or the PTR have a reduced proc chance while hasted to maintain a constant PPM.
Instant attacks use the unhasted weapon speed to determine proc chance.
Also, see
post 121 for a more detailed thread summary.
Here's the data (error bars are one standard deviation):
