If I may derail thread a little more:
I'm also against existance of chaos light cruisers. If they really want one, there's an option for a CSM strike cruiser. They just don't really need CL's. There's nothing chaos fleet can't do without them.
So, apart from treating them as a little flavour, there's one use of them that makes any reasonable opponent hate them with burning passion: Light Daemon Cruiser. Cheap enough to never materialize and just provide stable -1 Ld for enemy ordnance ships, fast and mobile enough to make their escape impossible and impervious to any harm. True, Slaanesh Daemonbombing got cut down a bit with marks not working while spectral, but this thing is cheap enough to be worth it even with simple -1 Ld. And if you get two of them, because why not, they're cheap, we're back to crippling ordnance heavy fleets.
And if they're marked and do materialize.. well, think of one with Siren's Summon. Yes, it will probably die right after materialising, but well, that's one enemy turn guaranteed to be ruined. And if it manages to survive that one turn, crucial enemy ship is without orders for two full turns.
So, yeah, maybe we should discuss moving chaos CL's to ASC?