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

Improved Power Word: Shield

Increases the damage absorbed by your Power Word: Shield by 7/14/20%.

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 damage absorbed by your Power Word: Shield by 5%.

Data	Classic	Forever
effect 1 value	5	20

What Blizzard said about Improved Power Word: Shield, each line checked against the files.

Matches the files
Improved Power Word: Shield: Slightly more increase per talent point.
The files Classic gives 5/10/15% over 3 ranks; 70245 gives 7/14/20% (spell 14748).
Improved Power Word: Shield Class deep dives: Priest and Warrior

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