With the new chaos space marine codex release, demons were neutered. Most players simply feel they are not even worth taking. I totally disagree. They are a super cheap and fearless. They hit like a assault marine, and have a 5+ I save.
Most importantly they summon. Summoning works like deepstriking near a teleport homer but you get to assault "if you can". The trick to using daemons is putting them in situations where they can assault the turn they come in. Bikes, terminators, personal icons, and rhinos can all really help you deliver the daemon to the fight. Also it should be mentioned, in 4th ed daemons are risk to take because of escalation. Thus you have to rely on infiltrators which eats up points and hurts you in an alpha. 5 edition kills escalation and completely empowers the daemon.
So to kick off the new demon bomb I started thinking about what are the best size units are now that there is no god flavoring.
So without further adieu: Circumference = 2 Pi X R
- Squads of Five give you the max number of scoring units but are easy to kill.
Beyond that with deepstrike you get one full ring around the center model at 7 models, so 8 would be a good squad size as it gives you an extra inch on the charge, and you get the boon of needing to lose 5 guys to fall below 50%.
To get an additional inch you need to bump the squad up to 19... So you might as well go with twenty.