Yep, doesn't say but it's not far fetched either. And another explanation might be that the AM in the Eye reverse designed the engines. Hey if they can build Acherons, I'm sure they can build Slaughters.
That's always possible, but frankly I suspect that most of thier engineering was given over to the Planet Killer.
CLs are functionally useless for Chaos. Chaos captains are often lone wolves and also megalomaniacs. It behoves them to have a shp of greater tonnage than the what the IN could use to catch you. It also suits the psychology of a power hungry rogue or Chaos captain to take larger ships.
Light cruisers would not appeal to a captain, would provide little utility to a warfleet and is too much on even terms with the enemy as a raider. If you had the choice between a Dauntless or a Slaughter to captain which would you choose? If you said 'Dauntless' you wouldn't be captaining it for long. 
The problem with that is: A) There is no possible way there are enough slaughters for every would be chaos raider. And it's entirely possible that some would be warmasters would happily punish underlings by giving them command of a light cruiser and putting it on patrol around their holdings. Also, remember that not every hoard of chaos space marines is allied with Abaddon's warfleet. Many of the legions did break up, with whatever would be warlord grabbing whatever he could when he left. Someone will have gotten the short straw.
B) In the case of at least two legions, Alpha Legion and Night Lords, the Dauntless would actually be preferred for infiltration purposes. In fluff Night Lords have access to (your favorite) several lance carrying strike cruisers. (To really twist your noggin, one of them is still used by a former member of Night Haunter's inner circle). I think that you forget that while, most of chaos are crazy megalomaniacs, you also have groups like Night Lords where going insane and embracing the ruinous powers is seen as a weakness, not something you willingly embrace. When it happens to one night lord in fluff, his terminator bodyguards start talking about who they should select to replace him, and this seems to be a normal state of affairs!
Further: if all chaos captains were megalomaniacs, fleet operations would be impossible. It would be like herding cats. Particularly since they could just
leave. It's happened before to Abaddon's fleets and in the past there has been nothing he could do about it.