From landsoul's spreadsheet, if I get the shoulders I loose 80 dps, while the belt will net me around 100 dps increase. Thing is, shoulders would be my third tier10 piece and then I would be 1 piece away from the 4 piece bonus.
So the question is, should I go for the immediate 100 dps increase, or go for the 80 dps decrease aiming for a better result in the longer term?
Any high-end fury I've seen gets the shoulders as part of their 4pc. If they're just going 2pc I usually see helm/shoulders too. The belt is really nice but there's quite a few other solid options like the belt off Dreamwalker, leather belt off Putricide or plate belt off Rotface 10/10H. There's also a really nice mail DPS belt off Blood Princes I believe? Comes down to shoulders being best option and belt being one of many good options.
You don't want to lose your 2-piece T9 until you can get 4-piece T10, that is why you see a dps loss equipping the shoulders in the spreadsheet. Save your emblems until you can pick up the shoulders and the chest, and wait it out for a better belt to drop. Even the leather belt from Deathwhisper 10-man would be a nice dps increase for you in the mean time.