I was seeing DB at ~50% before, I thought for a while it was every other autoattack. Fel mastery is a buff unless you have a really low crit rate, but Prepared needed a nerf. I gave feedback a while ago that it was more than twice as strong as Appetite. I don't know how much fury DB gives, though, but it replaces bite so until we're in T19 4pc it won't be likely a DPS increase over either of the others.