Saw your deck through reddit. I don't want to get your hopes up, but you're going to have a hard time with this deck. Firstly, drop Polluted Delta's & Underground Seas for Misty Rainforest and more Watery Grave . This will bring you up to modern legal where the deck will fair much better.

Mill isn't competitive in standard. You'll find most say it's not competitive in modern, but personally I've had very good luck and don't think it's nearly as bad as people say. It's not quite competitive yet, but it's definitely on it's way. Lastly, mill is competitive in Legacy, though it takes on a mildly different form. I'll elaborate at the end of my suggestions.

Drop your 2x Traumatize for another Glimpse the Unthinkable and Mind Funeral . Traumatize is good early game only, so if you don't get it, it's a really bad draw later on.

Drop both Breaking for another Wight of Precinct Six and Snapcaster Mage . Drop 1x Oboro for a Rogue's Passage for your Consuming Aberration. Drop Doom Blade for Go for the Throat , which is a bit more universal. Drop both Crypt Incursion and Thought Scour for 2x more Go for the Throat and 2x Rapid Hybridization . Crypt Incursion works against your Wights, they should be in the sideboard if anything. Rapid Hybridizations shouldn't work against you if you get your Wight's out and the mill rolling. If you prefer a more beatdown oriented mill experience for your opponent as I do, replace your Hedron Crabs with Jace's Phantasm .

So nextly, if I play mill, I use it to supplement a beat down deck first, win condition second, because it's easily disrupted. The changes I suggested made the deck modern legal and a bit more universal. Which is what you want, right? Well, with either iteration of the deck, how would you combat Leyline of Sanctity? Spoiler, you can't. Not with what you have. Right from the git go, you can't do anything. Your creatures will never grow up big and strong, and you're basically at the mercy of your opponent. Elixir of Immortality, Emrakul, the Aeons Torn , Aegis of the Gods, there are lots of ways to screw you. Treat mill like burn, except you need to (realistically) burn for 60, anything that reset your count is absolutely detrimental. This is why I play beatdown first, mill second.

So, let's talk about sideboard. I'd consider 4x Boomerang , 4x Surgical Extraction , 4x Mana Leak , 2x Hurkyl's Recall , and a Kira, Great Glass-Spinner . These should give you the ability to deal with most problematic decks you'll come across.

For other thoughts, I actually prefer Esper or BUG mill in modern. Either gives you better access to artifact/enchantment removal. Green gives you access to ramp (I prefered Birds of Paradise ) and the great Tarmogoyf . Esper gives you access to Path to Exile , which you then could punish them with your Archive Trap .

Oh, for Legacy Mill, look into 'High Tide'. It's a combo deck designed to float enough blue mana for cast a lethal Blue Sun's Zenith . Pretty cool stuff.

Let me know if you have any questions and good luck!

Yeah. One of three things is happening here:

(1) You added Underground Sea and the fetch-lands to this list, not knowing how much money they actually cost.

(2) You will be proxying those lands for non-tournament games, at which point you should know you're a terrible person for proxying dual-lands for casual, friendly games.

(3) You actually have those lands but play casually, at which point you should just sell them and buy every casual deck you'll ever want for the rest of time, forever.

Thanks for the feedback, it's truly appreciated!