Diamond Slash is it worth the 50 spec points?

[ddt73]

I was wondering is it worth speccing all the way up to lvl 50 in slash to get Diamond slash?

Is the skill worth all the points?

I have a paldin, I'm trying to decide if I should spec all the way to 50 in slash to get this skill, or put the extra points in parry/shield to improve my defense.

All feedback welcome. I thank you in advance.