I know people are jerking you back and forth over what to add/remove, etc. but I took one look at the deck and thought that urban evolution should not be in it. 5cmc at sorcery speed doesn't do the rest of your deck mechanics any good - however, I DO believe you need the card draw/dig capabilities to be able to get your combo going or restart it when something gets taken out. I think Izzet Charm would substitute well for the urban evolution. 2cmc at instant speed with the option to counter a non-creature spell, deal 2 dmg to a creature, or draw 2 then discard 2. This should give you more flexibility.
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This deck looks pretty good, the only thing I might change would be to cut down on your mana fetch/producing cards and/or slightly reduce the number of lands you have in the deck. Mainly because the bulk of your deck is comprised of 1-3 converted mana cost cards and you could add a few more creatures to the deck this way. Nice use of threshold and dredge though.