Salvation was changed because
A) It made Paladins ESSENTIAL to raids, and they wanted to get away from any one class being absolutely essential in a raid.
B) All the DPSers who would rather have something to buff up their damage were forced to get this. While it's nice for threat and it technically gives them more damage output, people generally like seeing bigger numbers. Now we don't have to worry about people going "I don't want salv, I want Might! (Kings, etc...)"