Yeah, it roughly adds 25% more threat (my bad on my previous post, I missed two words on my statement about threat) to us but it doesn't double our damage, like you said in a previous post, since it does 50% of our damage and certain abilities does even less damage (namely HS).
I still think it's better to save it when you really need as a defensive CD but you can safely use it if you know you'll need it after the CD would be over.