The purpose of Comp is typically to force players to run something outside of the overplayed flavor-of-the-month armylists. No one wants to play at a tournament where half of the players are running the same list. But if you want variety, why include Comp penalties for old, underplayed armies?
Da Boyz comp, for example, is great for stirring the pot among top-tier 5th edition codices, but it completely screws certain armies that were already going to be underplayed at a big competitive event (Chaos Daemons, Sisters, Necrons, Eldar, etc). Sure, some of the penalties are halved for certain codices (Necrons, Sisters, Dark Angels, and Black Templar for da Boyz), but why even have these penalties at all?
Frankly, there is no reason to penalize someone who shows up with Necrons. I doubt you'll have problems with a surplus of Necron players. If the point of comp is to encourage variety, it just seems counter-productive.