This change seems a bit puzzling for prot in 10.2

[Westly-frostmourne]

I think the 15% is for ret. Not Prot.

@Linxy

Retribution

• Flash of Light healing increased by 35%.
• Word of Glory’s mana cost has been increased to 15% (was 10%).

Source: Undermine(d) Development Notes - In Development / Undermine(d) PTR Discussion - World of Warcraft Forums