Mill is cute, but I don't think it's competitively viable. It really only has favorable matchups against decks that generally run large hands, like handlock, freeze mage, and control warrior. But with decks that can dump their hand really quickly like zoo, shockadin, or backspace rogue, you're just dooming yourself.
At the same time, competitively only zoo is played and even that isn't played that much. It's a lot of miracle(when not banned), ramp druid, token druid, handlock, midrange hunter, shaman(as a counter to other stuff mostly) and control paladin(generally with hefty dose of heals).
If you mean on ranked though, lots more zoo yeah. And mill does pretty bad against zoo. Can still win every once in a while but bad matchup usually.
I played druid and rogue mill a decent bit and druid mill is more consistent and safer, you can use healing touch to heal up, the hero power+claw+bite let you remove stuff while armoring up and naturalize is just fucking awesome since it's like the best removal in the game if you're trying to mill. However, it's also the least agressive milling deck out of the 2 and you self mill almost as much other than naturalize and the mobs so it's a fine line.
Rogue on the other hand with sap and vanish can keep destroying key cards while milling, and the burst mill to fill the opponent's hand is a lot higher with shadowsteps than with brewmasters and lets you oracle much earlier. On the other hand no way to recover from a bad start with rogue so it's less consistent since if you lose early due to bad draws or whatever that's generally it.
Neither deal particularily well against aggro. I guess you could build druid to maybe be better against aggro though. In mine I had a few of the tech cards I usually use in my normal deck like a pyromancer and stuff but it wasn't enough.
In the end the main issue is still that even with the new cards, it takes a long time to mill a deck and you have to not die during that time considering the opponent's hand is always full. The fact you have to bounce your oracles back and forth to actually be able to mill at a decent speed is a big weakness of the deck. If there were more milling cards it'd help, especially faster ones(deathknight and dancing sword are alright but they're kinda slow to mill). Asymetrical mill cards would be the best, for example something where you gain life and they draw, so you don't mill yourself in the process.