this is the deck I used to beat Heroic Chromaggus. early game use Zombie Chows or Doomsayer to clear Faerie Dragons. Mistress of Pain + Demonfire (and later Demonheart) are also prime keep opportunities to clear those early drops and help counteract if not completely negate the Red Affliction. Use Soulfire, Succubus, and Doomguard to hopefully discard Affliction cards that are starting to stack up in your hand, and use lifetap when possible to fill your hand so that you can't get new afflictions. Use Floating Watcher to turn Red Affliction into not just an advantage, but a win condition!
Always get rid of Bronze Affliction no matter what, unless he's already top-decking. Almost as important is getting rid of the Black Affliction, especially if you have a Blue in your hand already. If you don't have Blue, you can usually afford to let Black sit a turn if absolutely necessary. Having him give you Green is ideal, as is Red once you have a Floating Watcher out (or at least a buffed Mistress of Pain).