SatakOz

I wouldn't run more than one Dregscape Zombie, I have a single Fatestitcher in my deck as an "Insurance Policy". Though seeing this deck has really tempted me to switch out for Red.

It's not about value here, it's about comboing out by bringing back 2 Gravecrawlers which then consequently brings back all the Vengevines you may have in your graveyard and killing them promptly with usually 12-16 power of hasty guys.

Dredge doesn't use Sac Outlets, it uses Dredge cards to put things straight from the deck into the Graveyard, and discard to put them from the hand to Graveyard, then bring them back with effects.

I considered going for Red when building my Dredgevine deck, but ultimatley went for Blue for Hedron Crab, Fatestitcher and Magus of the Bazaar.
How is red working out for you? I like Lightning Axe and Faithless Looting but couldn't justify them to myself. Might be useful for you to include a Dregscape Zombie or some such for when you want to "Go Off" but don't have the Lol Trolls or another Zombie to use Gravecrawlers ability.

Have a Similar Deck myself, mine is more focused on ramping and making big Dauntless Dourbarks and Dungrove Elders, but your build might work.
I run Corrosive Gale in my Sideboard to deal with Flyers, In a pinch, you can pay the PHyrexian Mana with 2 life to use all your land to wipe them out.
Also, Reach of Branches is awesome in any Treefolk Deck if the game goes long, Bosk Banneret makes it cheaper, you get more Treefolk for Dauntless Dourbark, and as long as you keep playing forests, it keeps coming back to your hand!
Hope this helps!
http://www.mtgvault.com/satakoz/decks/entmoot/

Started building a similar deck myself a while ago. Have you maybe thought about Ashen Rider? Works quite well with Rescue from the Underworld. I also played around with Abhorrent Overlord, even if you use Whip of Erebos on it, it leaves behind Harpies. Nice deck though :)

Except there aren't Izzet Dual Lands in Theros.

Try Thirst for Knowledge, really good card advantage in an artifact based deck.
Have a similar deck myself, though mine is white and more control based
http://www.mtgvault.com/satakoz/decks/our-name-is-myr/

I'd reccomend bumping Manaweft Sliver up to a 4-of, just because it is really good acceleration and fixing, which a 3 colour deck needs

Technically, I don't think you can do this, as you can't cast Undying Evil in response to the opponent's choice, you'd have to cast it before Vexing Devils ability resolves (and any choice is made) in which case, your opponent is most likely going to let it stay. This is because the choice, and then the act of sacrificing the devil are all the same ability, not two separate ones, so there is no time to cast an instant

Have a similar deck myself, your deck itself seems fine. I'd swap Shatterstorm out of the sideboard for Shattering Spree, with the amount of R you're generating, it's pretty much the same effect, plus you don't have to "waste" 3 mana if you only want to destroy one artifact.

http://www.mtgvault.com/satakoz/decks/oncoming-storm/

My Girlfriend runs vampires, I think they're viable in Standard, maybe even modern. Bloodline Keeper and Stromkirk Noble are really good Lords, and Olivia Voldaren is powerful. Rakish Heir also provides a powerful Lord effect.
Here's her list, though hers isn't Standard. http://www.mtgvault.com/sapphire616/decks/the-dark-brotherhood-2/

I suppose, it's a little bit risky. Here's mine:
http://www.mtgvault.com/satakoz/decks/night-howl-2/

The deck seems pretty solid, Blasphemous Act seems a little... useless, my werewolf deck is pretty much the same, except I use Pit Fight as removal.

I would agree with the Nivmagus Elemental, they're really good, and can get quite bonkers. Plus if you Dragonshift it, it keeps the counters.
Plus if you're playing against control and your spell gets countered, you can just feed it to your Elemental

Built a similar deck myself just a few days ago, and have been playing around with it. Has a few cheap creatures that react to spells and a few pump spells. Take a look and see if you have any good ideas :)
http://www.mtgvault.com/satakoz/decks/izzet-thunder/

I feel like Legion Loyalist and Hellrider are being wasted here. They're only useful with lots of creatures, and there's barely any here, yea I know you've got Assemble the legion, but that's only a late game thing whereas Legion Loyalist is a one drop. You've got two options, really, go purely aggro, which would utilise Legion Loyalist and Hellrider better, or pure control, which the deck seems more geared toward, for which you'd greatly benefit from Augur of Bolas and Restoration Angel.
Hopes this helps, and doesn't sound to arsey. I'm not trying to be an arse, I'm just having a bad day.

You already have Arrest, I'd maybe suggest Oblivion Ring then, or if you're willing to splash some cash, Detention Sphere

Oh god. I feel your pain. My Girlfriend has those two decks, effectively, you'll be wanting board sweepers like Supreme Verdict, unfortunately a quite expensive card. I find with a lot of Aggro they play a lot of non-flying so, stuff like Lyev Skyknight will really help, maybe look at some flicker cards from Avacyn Restored to re-use enter the battlefield effects.

A few tips for deck building:
1. Don't have many 1s or 2s of cards, 3s and 4s are best, it helps ensure you draw what you need when you need it., for your big end-game cards though, 1 or 2 copies is enough.
2. Dual Lands are usually useful, probably the gates, in your case.
3. In a 60 card deck, run 24 lands most of the time, some deck you can get away with less, but looking at this, you'd probably want 24.

Sideboards, I can't help you with, I need to learn how to make them myself, though I will say Azorius Charm is a really good main deck card, so it shouldn't linger in your sideboard