Breaking / Entering instead of Mind Sculpt . Same mana, 1 more card milled.

Tragic Slip is not such a good card in this deck since you have no sac outlets nor other removals. Replace it or add to the deck some removals like Victim of Night Ultimate Price and/or Devour Flesh that will allow you to manage the creatures your opponent will trow at you.

Increasing Confusion is much less random than Mind Grind and can be cast for double power from the graveyard.

If you are having life problems (facing fast aggro is always difficult for a mill deck) you may consider adding Crypt Incursion to the sideboard.

Against control decks having Negate or Dissipate instead or alongside Spell Rupture may give you a big edge.

I'm sure you already know and it's just a budget problem but you should run 4 Drowned Catacomb and 4 Watery Grave instead of the Dimir Guildgate

Wow, thanks a ton for all the great suggestions! I'm waiting on getting my hands on those Dragon's Maze cards until they come out and the land thing is definitely a budget issue, but the Tragic Slip suggestions is a very good point. Much appreciated!

If your primary win con is to mill people to death you probably want a playset of Devour Flesh . You also want some kind of wrath effect like Mutilate . If you are splashing white you can go for Supreme Verdict which is one of the best mass removals in standard at the moment. Also Terminus . Otherwise, try playing Gloom Surgeon to hold off early aggressors.

You may want to consder changing it into a Green-blue deck with a splash of black. GUb Will allow you to power through the early game, setting yourself up with the mana to obliterate the opponent's deck with a Mind Grind , Increasing Confusion , Dreadwaters , or a combination of all. This will also give you the ability to deal with Artifacts & enchantments. However, it will turn Consuming abberation into a 1-of and require you to use different removal (for example, Putrefy ) and counterspells (spell rupture would get better though.).

If you want to stick with UB, definitely add some Blustersquall s. It'll act as a Sleep when used on your opponent's turn or be used to get your Chainsaw-wielding creatures through. Also, Speed bumps like Fog Bank may also work.

I think Breaking / Entering and Mind Sculpt . Direct Mill is the way to go. I am leaning away from Milling "until you draw a land". In a typical deck that will average at about 3 cards.

I have used Vampire Nighthawk as a nice creature to keep you alive.

My favorite "indirect" removal is Death's Approach . 1 mana and it works as long as you have started to Mill.

Also check out Dimir Charm . I found Far / Away is useful in the mainboard

The problem with Mill decks is that you have to mill 60 cards from your opponent while your opponent only has to deal 20 damage to beat you. Consuming Aberration is a great powerhouse that'll end you games if put on the field. That should be your primary win-con. Think of milling not as your way to win, but as a way to help you win. Essence Harvest or Artful Dodge would benefit you greatly with all the (soon-to-be) powerhouses

solid mill +1

I apologize if my suggestions repeat anything said above, but I'm way too lazy to read through it all. Right now, I think there are three main outlets for mill in standard, and any mill deck should try to stick to one of them to maximize potency. They include:

1. Creature based mill -- Uses a lot of the powerhouse creature mill cards, such as Consuming Aberration , Duskmantle Guildmage , Mirko Vosk, Mind Drinker , and Jace's Phantasm . I do like to see the Undercity Informer // Undead Alchemist combo in these decks as well.
2. Spell-based mill -- Relies mainly on utility cards like Grisly Spectacle , Thought Scour , and Psychic Strike . There should be a lot of control-based mill cards in these decks, and a few creatures to help lock down the battlefield. My deck, Perfection of Milling, would be an example of this.
3. Unblockable-mill -- More of a janky mill deck. These will use Paranoid Delusions ciphered on unblockable creatures such as Invisible Stalker . You could also run Artful Dodge to ensure Mirko Vosk, Mind Drinker gets though. If you want to go all out "Johnny," find a way to give Mirko double strike :P I haven't played a deck like this before, so I'm not even sure if it's viable.

With that said, I think your current build could be steered towards Type 1 or Type 2. I think a creature-based mill running off of the Undercity Informer // Undead Alchemist combo would go against aggro the best, but it really depends on your meta. If there's just one or two decks around that give you trouble, but you fair against the rest just fine, then leave the deck as is. A great T/O user and magic player once said (paraphrasing, so bare with me) that a deck that tries to beat everything will be good at nothing.

More specific to the build, I'm not sure that Spell Rupture is a great fit, since it doesn't have a mill aspect to it. I'm also weary about Snapcaster Mage , which could be a little out of place here (or as out of place as a Snapcaster can be). Wight of Precinct Six is a very conditional mill card - it's great against aggro builds, but provides no evasion, and is pretty useless against decks that don't run many creatures.

Some cards you may consider are Mind Grind (if you go towards a more spell-oriented build) and Codex Shredder . The latter is one of the most vital cards in my mill deck. Not only does it serve as a decent recursion engine, but also serves as a small mill source, which, although rarely, can change the game completely. Last but not least, Dimir Charm . It''s good in so many ways - as a counterspell, as a mill spell, as card-fixing spell, it's very very good.

I apologize for such a lengthy post but I hope that some, if not all of it helped you with this deck. Feel free to ask any questions about what I've mentioned. I sometimes miss these updates on decks, so feel free to post on my wall with specific questions as well. +1.