When I first saw your deck I didn't like the look of it. But it seems to work quite well. A little slow to get on the Darkness production sometimes, though. I thought of using Hax Shield but never tried it, but as I said your deck seems to work. Hax Shield gonna hax. I like the little poison boost as well.
Initially the Bonewalls were meant to be paired with the Parasites, but really they're still good without something to generate death effects. As they're a "block-all" kind of shield you don't need to get them out especially early, it can be used as a sort of 2-3 turn Dim Shield. I never found that I couldn't play them, and you need some sort of stalling factor with poison as your main attack force.
My deck is fairly heavy on Darkness but depending on the enemy deck you need to play your darkness cards soon.