I did a quick search, Spiderman and the opinion seems to be that Necropotence needs to remain restricted. Two of the sharpest minds in the format: Steven Menendian and Phillip Stanton (Smmenen and Dr. Sylvan, respectively) think that Necropotence is one of the cards so broken that it should never be unrestricted. I tend to agree with that sentiment. A card that can be cast first turn off of a Dark Ritual and which immediately draws you 15+ cards is excessively strong. Even though you have to draw them at the end of your turn, for a deck like Worldgorger Dragon (example), discarding 13+ cards isn't a big deal, if it means that barring a really great play from one's opponent, one wins the following turn. Although Necropotence would help mono-black control, it must remain restricted, since it helps combo at least as much, if not more. Historically, that has been the purpose of restriction: keeping combo in check so that control can actually be fast enough to beat it.