You guys are pretty weak in my opinion, I support OP because it is an option. For some reason you all clearly embrace restriction and a lack of options. He wants to use cannith crafting as intended, and clearly this oversight is preventing what should be a standard game function. Crafting seeker on an item that can be considered an off hand weapon, that takes the slot a shield would, that is treated as a trinket for crafting purposes does not seem like something requiring restriction. It even comes on other rune arms. There is no reason to disallow the ability to craft seeker on your rune arm, short of laziness.