WoWDB

Proc Information:

• 0.56 RealPPM on landing harmful abilities and spells, and melee/ranged abilities and swings.
• 22 sec ICD

Stacking:

Ghostcrawler: Renataki’s Soul Charm, Fabled Feather of Ji-Kun, and Wushoolay’s Final Choice all proc a buff that automatically gains a stack every 2 sec (and have ICDs such that it’s not possible for them to proc again while they’re already up). Also, this is a good time to note a nuance with Delicate Vial of the Sanguinaire: its proc’d buff can stack just like Talisman of Bloodlust, Primordius' Talisman of Rage, and Gaze of the Twins, up to a max of 3 stacks. We didn’t note that in the tooltip since (apart from tanking large packs of mobs), it would be extremely rare for it to happen.

This means you gain 1,333 Agility when it procs. Set that to 0 seconds. You then get another stack every 2 seconds, ending with 10 stacks. The average value over the 20 second duration is 7,331 Agility.

1 stack =   1333
2 stacks = 2666
3 stacks = 3999
4 stacks = 5332
5 stacks = 6665
6 stacks = 7998
7 stacks = 9331
8 stacks = 10664
9 stacks = 11997
10 stacks = 13330
Average 7,331

Here's the blue post on proc rates.