Priest talent · row 3 of Shadow, from level 20 (15 with Talented 5/5) · Physical

Improved Psychic Scream

Reduces the cooldown of your Psychic Scream spell by 2/4 sec.

Game files · build 1.60.1.70245Read from the WoW Forever beta client, build 1.60.1.70245.

Compared with Classic

Classic tooltip

Reduces the cooldown of your Psychic Scream spell by 2 sec.

Data	Classic	Forever
effect 1 value	-2000	-4000

What Blizzard said about Improved Psychic Scream, each line checked against the files.

Matches the files
Improved Psychic Scream: Blackout is now a pre-requisite.
The files Talent edge 136300 runs from Blackout to Improved Psychic Scream; Classic had no prerequisite.
Improved Psychic Scream Blackout Class deep dives: Priest and Warrior

69876 Sep 16First beta build we archived. No changes in the client files since.