At the moment, the gargoyle backing to me seems to be too high a smith DC for what it does, and possibly tan DC as well. Gargoyles are easy to kill, show up in decent numbers, and the bonus is more suited to lower level characters that could be acid arrow spammed in the thouls cave. I think the bonuses are fine, but an adjustment in the smithing DC might make it more sought after, since it could be a lower cost alternative to the scrag backing, which is my favourite at the moment.