Skills modified on PVP

[caramel0rar0 0]

Hello guys.

So I have got a big question about skills that are diferent from PVP to PVE. 

For example, Focused will (https://www.wowhead.com/spell=45243/focused-will) decreases damage taken by 15% (stacks up to two times). But if you're in PVP and you read the skill tooltipe it says 15% but if you read the buff given it says 10%.

How can I know which skills change on PVP? I think there should be a list with all skills that change. 

Thanks. I wait for your answers!