Only times I know to use it is for engineers and bards full supports for PvP, so they can play faster due to lower gcd's.
Also demonologist tanks need it to spam Torturer's Blades faster, that keeps their shield up easier.
Thank you for your post. I have read through several similar topics! However, your article gave me a very special impression, unlike other articles. I hope you continue to have valuable articles like this or more to share with everyone! foodle