This deck pulls in a couple differant directions.  If going red burn, drop a lot more into red burn.  Shock, Sizzle, Fireballare cheaper better ways to keep Chandra's Fronex out of your graveyard.  If doing that, why not find a way to get Guttersnipein to really keep the damage rolling?  If you want green beats and Garruk's Horde at the top, look to more efficient creatures to cast so you can really flood the battlefield when he drops.  Dragon hatchling, Sacred Wolf would be easy and good to add to the battlefield.  2 Indrik Stomphowler is a fine replacement for 1 naturalize, and adds more warm bodies to the deck.  Pick a direction (red burn, green beats) and go with it.  And if you want to really mix the two, the green will do enough damage to someone's face, so focus the red on burning out defending creatures so that your own can connect.

*slow clap*