Phyrexia mill

Horrifying Revelation may actually not be a bad option to run here. It gets a card out of their hand, and helps a little bit with the milling. I'd also look into Archive Trap, since almost any deck searches nowadays. Also, think about running a few of fetch lands (Marsh Flats and Misty rainforest, for example) for extra landfalls, and if nothing else, terramorphic expanse serves this purpose.

Add Mindbreak Trap to your sideboard - with all the fast red decks playing multiple spells early in the game and depleting their hand this trap should slow them down just a bit. It is a mythic, but not in demand right now, so easy to obtain for under two dollars.
There is also a black rare, Memoricide, allows you to remove a pesky planeswalker, or an anti-milling card from their hand and deck, such as Elixir of Immortality or that nusance Eldrazi card they will sideboard in against you - Emrakul the Aeons Torn.
A card to help you with creature removal, besides Blacksun's Zenith, is Consuming Vapors - it nabs two of their creatures or makes them hesitiant about playing one on their turn because of the rebound mechanic. But it also nets you some life which helps you hang around to mill them.
Horrifying Revelation doesn't give you enough control - I would opt for Duress in the sideboard or the very annoying Inquisition of Kozilek - an uncommon black sorcery spell from Rise of the Eldrazi and it only cost one black mana to cast so if you are first you get to look at your opponent's hand and quickly size up the threats you will be most likely facing which helps you plan your strategy accordingly - including sideboarding. Also it is much more distracting and annoying to your opponent when they watch you mill through their hand besides their deck - Horrifying Revelation lacks puch in that department. A card that shocks your opponent may cause them to make play mistakes as their mind is distracted worrying that you know what is in their hand. It will also help you know which creatures to save Go For The Throat for too! since i mentioned Go For The Throat you may want to balance it or have an alternative removal card in your sideboard for large artifact creatures, etc. Also the white weenie/artifact decks will make your Go For The Throats useless.
Also Haunting Echoes makes a very good sideboard card. While I am thinking of M11 cards, the Diabolic Tutor should not be over looked to get the right card for the situation into your hand, especially since your deck lacks card drawing which means your opening hand and first 4 draws will probably determine your fate right out of the gate.
Finally, your sideboard may want some sort of "bounce spell". You should experiment there, but blue has quite a few: Unsummon M11, Disperse SoM, Regress RotE, Aether Tradewinds W, and Into the Roil Z. For your deck, since your deck lacks card drawing I suggest Into the Roil the blue instant from Zendikar block because of its kicker which nets you an extra card. If you do not go for that then an alternative is a spell that can bounce back a painful man land into your opponent's hand depriving them of mana for a turn and preventing them from attacking you with it for a turn or two. but a bounce spell can return an artifiact that has been proliferated with counters multiple times which makes your opponent start from square one! Aether Tradewinds, then, would be my second choice, possibly first because it can return one your permanents that has infect counters on it or even a pesky enchantment placed on it by your opponent.
Time is the name of the game when you operate a mill deck. You have to buy enough turns (how time is measured in MtG or by how many cards they have left in their deck when they play against you LOL) to cast your mill spells and to be able to draw them from your deck.
when you play tournament games be sure to play with pen & paper and make a note of the cards you mill into their graveyard or see in their hand. Keeping track of their hand size and asking them their hand size every third turn or so just to make sure it is what it is supposed to be - keeps them from making an extra top deck if you know what I mean, especially if they are feeling deperate. It alerts them that you are paying attention to the number of cards/spells in their hand.