Hearthpwn

Overview:
Abuse Maexxna's hero power to replay Duskbreaker each turn and keep the board clear, finishing off with Alexstrasza, Mind Blast and Lifedrinker.

Mulligan:
Mulligan for Duskbreaker .

Early Game:
Draw with Power Word: Shield and use your hero power and/or spells to heal.

Mid Game:
Once you have a dragon and Duskbreaker in your hand. Play it each turn. Maexxna's power is auto, and will always return Duskbreaker to your hand, ensuring you will be able to clear the board nearly every turn. From there, heal as needed. There is a ton of healing: Regenerate, Flash Heal, Power Word: Glory (best saved for the Stoneskin Gargoyles, since they will never die and will heal you each turn), Divine Hymn and Spirit Lash.

When the larger minions come down, the Twilight Acolyte can deal with them, or you can use combos of Duskbreaker / Dragonfire Potion and Holy Smite.

Late Game:
When you draw Alexstrasza, play her and then use the two Mind Blasts and Lifedrinker.

Note:
When you use either Lifedrinker or Twilight Acolyte, make sure you use them after playing Duskbreaker, otherwise she will kill them. This way you can use their battlecries each turn as needed for healing and/or neutralizing powerful minions.

Video:

My other Curse of Naxxramas decks:
Arachnid Quarter
     Anub'Rekhan (Taunt Warrior)
     Grand Widow Faerlina (Odd Warrior)
     Maexxna (Dragon Priest)

Plague Quarter
     Noth the Plaguebringer (Spell Hunter)
     Heigan the Unclean (Control Shaman)
     Loatheb (Control Priest)

Military Quarter
     Instructor Razuvious (Taunt Druid)
     Gothik the Harvester (Mill Druid)
     The Four Horsemen (Resurrect Priest)

Construct Quarter
     Patchwerk (Freeze Mage)
     Grobbulus (Odd Patron Warrior)
     Gluth (Divine Shield Paladin)
     Thaddius (Control Warlock)

Frostwyrm Lair
     Sapphiron (Fatigue Mage)
     Kel'Thuzad (Mill Rogue)