If the chaos gods didn't like you, they'd send along some of their agents to ... do something about it. What would a large pack of daemons on the hunt look like? I think they'd be quick and terribly dangerous. Therefore, this Apocalypse data sheet is designed to try to capture this rapid moving and sudden, high-impact danger. In giving all daemons fleet and the ability to charge after deep-striking, they're incredibly dangerous - and equal to Chaos Space Marine generic daemons. Therefore the cost has to be reasonably high, but not prohibitive. Nonetheless, I'm considering doubling it... Moreover, a maximum of 5 squads is imposed - a whole army shouldn't be made out of this idea.