Well, currently your deck is mostly a rush. Shields are great in principle in that they offer the most defence in a single card, but in PvP1 you're likely to run into either PC (permanent control), Momentum, big creatures and growers (Lava Golem, Forest Spirit) or decks that have more stall than you. As such, neither Skull Shield nor Carapace are very useful unless you pack 4-5 copies and more stall in your deck. If you want to turn your deck into a poison stall, I recommend changing elements to Entropy/Death or Aether/Death for Poison and Arsenic with Bone Wall and Pandemonium, or Arsenic and Fractal Mummies/Dragons with Bone Wall and Lightnings.
Air/Death also has a nice Bone Wall/Poison stall because of the multitude of CC (creature control).