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You might consider Inquisition of Kozilek or card:Mire's Toll for your one drop discards instead of Duress . Inquisition of Kozilek is good at getting the fast cards out of your opponent's hand early in game, while Toll is good midrange.
I'd only run Duress if you go up against a lot of creature control or burn decks where you play, but any of these three can do that job.
i recomend you to throw in Specters, for example Liliana's Specter is a good creature for a discard deck, also throw Quest for the Nihil Stone, they work awesome for my deck. If you want to throw in some red, i'd recommend Slavering Nulls and Hellfire Mongrel, they are really good cards for a discard deck, Guul Draz Specter is also a nice card
I see that this is an older post but I wanted to suggest that you take out Bojuka Bog . The reason being that if you are using Liliana Vess final ability, you want the cards in their graveyards to be there, not exiled so that you can gain control of them. However, it may be a good sideboard card in case your opponent has creatures in their deck that when put into a graveyard recycles it back into their deck like some of the large eldrazi creatures.