Card by card rating!
---LANDS---
Island - Seems fine.
Swamp - Seems fine.
Dimir Guildgate - Honestly you can do better, even being cheap.
Jwar Isle Refuge,
Tainted Isle,
Drowned Catacomb, etc.
Mistvein Borderpost - Counting this as a land since it replaces them. Useful for devotion, but that's about it.
Overall, consider running more than 22 lands. According to wolfram alpha, the chances of you having 5 lands by turn 5 is only 46.6%, which seems low given your number of 5-drops.
Proof:
http://www.wolframalpha.com/input/?i=probability+hypergeometricdistribution[12%2C22%2C60]+%3E+4
---SPELLS---
Keening Stone: Strong if it gets going, but 11 mana is a hefty price to pay for the first activation.
Mindcrank: Best with
Duskmantle Guildmage, where it goes infinite. Kind of mediocre otherwise.
Death's Approach: Run more removal - either more of this or other things.
Archive Trap: One-shot, one-opponent mill effects won't get you very far in multiplayer. That said, this thing is really funny to spring on someone.
Ashiok, Nightmare Weaver: This guy is good, but I'm not convinced you couldn't get more for your money elsewhere.
Haunting Echos: There's nothing quite like ripping a whole bunch of cards out at once, but I
wonder if something like
Surgical Extraction wouldn't
serve better here.
Mesmeric Orb: This thing is amazing. Consider going to 4.
Mind Grind: Pretty much the best one-use mill effect out there.
Opposition: Good card, but you don't really have any good ways of abusing it.
Dissipation Field: I would strongly suggest
No Mercy instead of this - think about what happens if you play against a blink deck and play this thing.
Propaganda: An excellent deterrent and good all-around choice, but do note that this does NOT
protect planeswalkers.
Rhystic Study: Draw is strong and you should run more of it. Be warned that I will focus you when you play these because I know how strong they are, and because "did you pay 1" is incredibly annoying.
---CREATURES---
Hedron Crab: I love this thing. Run the full 4, and consider things like
Evolving Wilds or
Dimir Aqueduct to trigger him more.
Cemetary Puca: This thing doesn't care about mill, and you have next to no removal.
Consuming Abberation: This thing is really strong, and does evil things with Phenax. Kind of awkward to have so many 5-cost creatures, but justifiable here.
Dreamborn Muse: Decent but not amazing.
Duskmantle Guildmage: Good all around creature, and goes infinite with
Mindcrank. Works best with triggered mill like
Mesmeric Orb and
Dreamborn Muse.
Fog Bank: Blocks like a champion.
Glen Elendra Liege: Good devotion enabler, and the pump effect is decent.
Lazav, Dimir Mastermind: This guy is cool. 3 is the right number since he's legendary.
Nightveil Specter: Good, but similarly to Ashiok, I think you might get more for your money elsewhere.
Sygg, River Cutthroat: You have minimal ability to trigger him yourself. How much can you rely on us?
Szadek, Lord of Secrets: Good finisher.
Oona, Queen of the Fae might also be good here.
Wight of Precinct Six: He can get big, fast.
Phenax, God of
Deception: Three is the correct number here.
By the way, I have a good number of cards for this deck I would be willing to trade. I'll bring up a list later, but it's something to keep in mind before you order.