I think its safe to say if you are playing a deck with the usual Tinker, Demonic Tutor, Vampiric Tutor, and Thirst for Knowledge and you aren't playing Time Vault and Voltiac Key then you built your deck wrong.
I don't think so. It's just not safe to say this. Many decks are competitive without Key-Vault and with Demonic, Vampiric, Tinker, Thirst.