So Mill has always a been a Meme Tier 4 deck. Brief over view of how I define tiers is as follows; Tier 1 are the most played decks on ladder comprising at least 10% of the Meta, Tier 2 are decks that target Tier 1 decks and can compete but may not be as played because of a weakness to a given deck or strategy, Tier 3 are decks that can have competitive draws but lack consistency as well as the shear power level to make up for their inconsistent draws, Tier 4 are decks with functional ideas but their draws never really work out and they rely on the opponent stumbling to win games, and last but not least is Tier 5 where the decks that just do not function in a realistic fashion because even when the opponent stumbles the deck still struggles to win.
As of the release of Flames of Xulta I can confidently say that Mill has risen to at least a tier 3 to 2.5 deck with my personal opinion being 2.5. This is because the addition of
Wretched Raven and
Kindo Shadowstep give you both another way to repeatedly mill the opponent and mass mill the opponent that isn't solitude.
Solitude is great as a finisher but it does nothing to change the gamestate if it doesn't just win the game. Before you had to rely on drawing two
Solitude, one to put enough in the void so that the second can win and the second to actually win. Now
Kindo Shadowstep sits and blocks, keeping you alive while he slowly ticks down to put enough cards in the void for a
Solitude win.
Mournful Deathcap and
Wretched Raven are threats that need to be answered before the void fills up enough for
Solitude to threaten lethal.
Shakedown and
Hailstorm are there for the early game aggro and role players.
Ice Bolt allows for some shenanigans where you bolt your own creature to play to a power and trigger
Mournful Deathcap plus it kills problematic units like
Sandstorm Titan. Desacrate is just a catch all answer.
Nocturnal Observer and
Honor of Claws are our card draw of choice. They both discard cards triggering
Dreamsnatcher and
Kindo Shadowstep while also discarding
Felrauk the Outcast and
Nocturnal Observer even makes the opponent draw a card and reduce their library. Every little bit helps. Speaking of
Felrauk the Outcast, this card is there to grease the wheels of the deck much like
Xo of the Endless Hoard. Basically if you get to discard him, they discard even a lowly power, and then trade with a kill spell or a unit then you basically got a 3 for 1. If that doesn't happen then you market him away. and if they happen to discard a non power card or you hit them when they just got something out of a market to play next turn, then you get the mill as gravy and possibly ruin their plans. But the point being, that last part is not why he is in the deck but rather just a happy accident if it happens.
All in all I think this is the best I can make it but I am not the best deck tuner. So feel free to to take this and run with it. The number one place for possible improvement would be to cut the Felrauk, Observer and Honor package for general purpose feln control cards like wisdom, champion, and bsh or something similar, but then its more Feln control with a mill sub theme and less a mill focused deck. At that point you are probably better off just playing Feln control.