I try to get into 15cm range of the enemy all the time. Not only is it good for Slaughters, Carnages, Dominators/Tyrants but also for the bigger ships, like Repulsives and Retributions. It can bite you in the bum, particularly with Eldar, if the enemy decides to go and blow up on you, but as a tactic it's well worth the risk. As for strategy, well I don't think it's necessarily true that you have to base your entire strategy around getting into 15cm range, for example I favour Carnages in my Chaos fleet as a great stand-off vessel. However, I think you have to factor into your strategy that the fight will end up in the 15cm range band and that not only should you be in a position to capitalise on this but against certain ships you should strive to bring it about. Against battleships for example, where long or even medium range sniping is rendered far less effective due to the number of shields they have. Again, Carnages serve Chaos well, being able to get close and unleash a devastating attack when there.