Well, because if you use your first Kingfist without an existing Golden Dragon, isn't it logical that your first Kingfist, which give you a Golden Dragon buff AFTER you hit, not receiving the buff from the Bracelet? Test with Z, you will see that all of your Kingfists will receive the bonus because you have an existing Golden Dragon buff.
I think they should look at WoW's Shadow Priest's Insanity mechanic. Basically it is similar to Shadow Slinger as in you have a resource bar you need to fill. For the Priest, once it is filled, you enter Void Form which makes you cast your spell much faster and they also have lowered cooldown. Once in Void Form, you will try your best to keep your Insanity bar from being depleted by using abilities that either fill it up or stop the bar from being drained. Your Insanity drain speed escalate through times so eventually you will be out of Void Form. So, my suggestion for Shadow Sling