was thinking about our 4 piece and yes it does look amazing, 40 seconds off our personal bloodlust, however in a average fight (about 6 minutes). Is it that big of an increase to get an extra 2 maybe 3 DS during the encounter over the gain if you were to use 2 set with off pieces for the huge haste/mastery gain?
I'm not the best at math, but you can figure out pretty basically that the 4-piece bonus is worth about 1200 average haste rating over having no 4-piece bonus over the course of only 2 minutes. But that figure would compound a bit more over multiple uses of DS in a fight.
(my math on the above might be really, really flawed :/ )
Also, the ICDs of certain Int procs tie in with DS under the 4pc cooldown a lot better than they do without it, so that alone is reason enough to want it. Optimal gear without the bonus wouldn't ever be worth losing said bonus at the same ilvl