It'd be nice if FRD ships only chase enemies they statistically loose against if there are no other allies who could do this job. So if you defend with fighters only, they would attack the bombers first, and then fighters and then frigates. But If you have a broad mix of ships, they will all try to avoid getting crushed.
If this is implemented, something must be done about some units that are labeled as "weak against everything, but stronger than the statistics say, especially in large groups" (-> eShuttle). Or maybe you just don't use these for defence and everything is just fine