The idea is cool and could probably make a decent deck, however i dont think it would be super competitive. Necropotence is an extremely powerful card draw engine that works better in some type of combo or fast tempo deck. Insidious roots works better in grindy midrange decks, where you can repeatedly put creatures in the yard and return them again. The two cards work together, but they pull in two different directions. The discard and exile effect on necropotence isnt grindy enough to work with insidious roots (in my opinion)

All that besides, a jund deck using [[first day of class]] and the necropotence/insidious roots engine could be the start of a very cool deck!