For a much, much cheaper way to defeat Maexxna - build a Warrior deck, stock up on Charge creatures, weapons and quasi-weapons or damage spells. Kor'kron Elites are your best friends in the whole wide world.
This deck has a few essentials that don't fit the theme, though, specifically Voodoo Doctors and Cleave.
Maexxna will often lead with some small-time minions like Webspinners, another Haunted Creeper or, if you're lucky, a Nerubian Egg. Yes, lucky - you WANT that threat of a 4/4 hanging over you.
See, here's the thing; it's actually fairly easy to get Maexxna to fill her entire board with 1-damage minions like spectral spiders (hit the first two Haunted Creepers with a Cleave) and Webspinners. At that point, there's essentially nothing she can do but keep punching you. The match turns into a damage race. If you can draw a Voodoo Doctor reasonably early, that plus the Warrior's armor power will drop her damage to at most three per turn, or two if she played a Nerubian Egg. A couple of Shield Blocks will give you a bit more breathing room, but if you really want, you can invest in heftier heals like an Earthen Ring Farseer (dropping her effective damage to one per turn), or even a Priestess of Elune to stretch things out indefinitely.
Once that's done, it's just a matter of throwing as much damage as you can at her. Maexxna doesn't have any heals in her deck, and she'll bounce your Charge creatures back into your deck every turn, so scrounge up every weapon, Charge creature and damage spell you can find - Bluegill Warriors, Wolfriders, Kor'kron elites, Mortal Strike, Heroic Strike, Fiery War Axe, Arcanite Reaper... Really, you can probably make this deck work without spending any dust at all.