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

Improved Disarm

Reduces the cooldown of your Disarm ability by 7/13/20 secs.

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

Compared with Classic

Classic tooltip

Increases the duration of your Disarm ability by 1 secs.

Data	Classic	Forever
effect 1 value	1000	-20000

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

Matches the files
Improved Disarm moved to Row 3 (Was Row 4).
The files The Oct 2 server hotfix (read from the 70245 client cache) moved Improved Disarm's node (105967) from row 4 to row 3 (PosY 3930 to 3330).
Improved Disarm Development Notes, October 1
Matches the files
Improved Disarm moved to Row 3 (Was Row 4).
The files Row 4 to row 3 in the 70245 hotfix (PosY 3930 to 3330), spell 12313.
Improved Disarm Warrior updates, October 2
Matches the files
Improved Disarm: Now reduces the cooldown on Disarm instead of increasing its duration.
The files Classic added 1-3 sec to Disarm's duration; 70245 cuts its cooldown by 7/13/20 sec (spell 12313).
Improved Disarm Class deep dives: Priest and Warrior

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