When I hit Captain and got my Defiant, I decided to try something. Instead of loading down with turrets in the rear, I opted for beams instead. This has actually proven to be really useful thus far in my build. Here's how I play it:
Before plowing into the fight, I hit all my buffs at around the 10 km range, and then blast at my enemy with my DHCs. If I'm fighting a single larger ship, I fly past and let my beams do the rest of the work. I can then come around, and either take em' out with my DHCs or a single quantum torp.
With multiple ships in the fray (or targetable mines/torpedos/fighters), I'll hit fire at will as I fly past allowing me to reduce the threat to my tail before I come around.
As well, if I'm taking fire from a boss ship, I can manage to survive by giving them a different side to shoot at without having to hit Evasive Maneuvers and come back while I wait for EPTS or Science Team to become available again. I can get rid of a boss a lot quicker this way.
I think at some point I'll switch back to turrets, as the forward firing power is nice (not to mention the fact that CRF works with turrets), but beams do feel viable in the rear.