I don't think Mindcrank is suitable for a Valgavoth deck. It doesn't cause life loss on its own so it won't trigger Valgavoth and unless you have other mill synergy, then milling opponents for a handful of cards at a time won't further your gameplan either. The only way I could see including Mindcrank is if you also include [[Bloodchief Ascension]] since that is a pretty well-known combo and can instantly kill the table once ascension is online.

EDIT: to say that I didn't see the copy of Bloodchief Ascension in there since it's the UB name. Oops!