I've done some fine-tuning and I think I've put together a much more competitive Dimir/Mill/Control deck that features Ashiok, Nightmare Weaver and Jace, Memory Adept.
Removal:
Far/Away: Great for Hexproof creatures and bouncing those pesky Advent of the Wurm tokens. Also, just a great spot removal in general.
Warped Physique: Great early on removal. If you can keep your hand count high, this card can even get rid of some of those pesky gods. This is hard to achieve, but I usually start to hold onto my land cards when I have 7+ on the board late game (in the off chance that I top-deck a Warped Physique.
Dimir Charm: Awesome card vs. Aggro decks. The card scry ability is helpful when you are trying to control (if they aren't hitting their land drops) or if you need to find a card yourself.
Hero's Downfall: Beast and a half removal. Very nice to have, especially with all of those nasty new planeswalkers. That's right, I'm talking about you Elspeth, Sun's Champion.
Liliana of the Dark Realms: She not only keeps your mana coming, but her -3 ability is great for removal.
The Control:
Thoughtseize: Excellent opening hand hate. Let's you plan your game and force the opponent to discard that damn Burning-Tree Emissary.
Cyclonic Rift: Can be a game changing play (this card has saved my ass more than once).
Psychic Strike: Control, mixed with mill. Plus, not restricted to 2U like most counterspells.
The Mill:
Jace, Memory Adept: My man. Pop him out and immediately use his +0 ability to pump Consuming Aberration and find a better form for Lazav, Dimir Mastermind.
Breaking: 8 mill. Nice.
Traumatize: Big time mill engine. Same benefits as Jace, Memory Adept and Breaking.
Ashiok, Nightmare Weaver: The star of the show. This bad boy is so great to get on the board on turn 3. Even with board presence, he can sometimes manage to do his job.
