Warrior talent · row 2 of Arms, from level 15 (10 with Talented 5/5) · Physical

Improved Overpower Rank 1

Improved OverpowerRank 1

Increases the critical strike chance of your Overpower ability by 25/50%.

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 critical strike chance of your Overpower ability by 25%.

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

Matches the files
Improved Overpower: Moved from row 3 up to row 2.
The files Classic Arms row 3, 70245 row 2 (talent position, spell 12290).
Improved Overpower Class deep dives: Priest and Warrior

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