Actually, I find that firing missiles in a chase fight is much easier than in any other situation. If someone is either on your wingman's tail, or attempting to flee on thrusters, and dodging, it is much easier to hit them with missiles than guns (might have something to do with my aim, but...).
When flying towards or perpendicular to the target, one has to time the launch right, and keep an eye out for incoming CDs, whereas, when firing at a receding target, you can launch at leisure, and watch your missile catch up and explode.