@chubbyrain1 I don't know that I agree with Tinker being an apt comparison. There are similar elements, if you're using Tinker to power out Blightsteel Colossus: you present a threat and give the opponent essentially a single turn to answer it. But that's not the common use of Tinker these days; instead it fetches Time Vault or Memory Jar and wins the game on the spot.
I can't speak for the power of 4x Necropotence in a Doomsday shell. If you think it would be absurd, I have no reasons to doubt it. I do remember playing against storm combo during the heyday of Dark Petition, and resolving Necropotence was by far the least-threatening thing my opponent would do after generating BBB. At a bare minimum you get one extra turn (and often 2+ turns) to fight back and I won a nontrivial minority of those games.