A few good mill cards are Nighthowler, Dreamborn Muse and Sewer Nemesis. As for fixing consistency I would make Phenax, God of Deception you commander. He's difficult to get rid of, and gives all your creatures mill effects.

With him as your commander, you can run more walls with bigger toughness to protect you, and mill easier. Some good protection is Riddlekeeper, Tree of Perdition, Hedron Crab.

With your extra draw power I'm surprised your'e not running Sphinx's Tutelage.

And as a mill deck you will most likely be an easy target because it takes so long to set up. Consider dropping high cmc cards for more early game stability. (i.e. Grave Betrayal) Yes it's a good card, but you could focus on more mill like Mind Funeral or Mind Grind.

Thank you, I will definitely get Sphinx's Tutelage, Tree of Perdition, Riddlekeeper, and Mind Funeral. Solid advice, was looking for something to take Grave Betrayal's place, along with a couple other cards.