Yes. It helps plenty. My fiend tends to be a 2-2.5 min CD with it rather than 4 min.
If a group is getting on to you for using PW:Shield as a Discipline priest (or jeez even a Holy priest), you have my permission to say "GC says you're doing it wrong."
"What... What the h*** was that?"
"I think I just saw a mountain kick a castle."
-exert from Sengoku Youko