I'm curious as to why you think that Vault/Key fits into this deck? I mean, the plan A is pretty fool-proof right? I dunno. It seems like it could be wasted deck space if you ask me. The tutor package isn't as robust because you are playing the 4 oaths +4 victory cards (2 dudes and 2 D-Breath). Does it really come up that often as a win con? Just curious.
-Storm
I would absolutely run Vault/Key in any oath deck that already runs Tinker. Sometimes its really hard to win by oathing (especially with White Leylines and gargadons out there) and Vault/Key give you a very easy Plan B to accomplish.