It would be an interesting plot point if a superadvanced alien race could fire energy weapons at warp while our heroes don't have the technological ability. That puts our heroes at one heck of a disadvantage. Alas, that's not the case with Starfleet (nor is it a big deal anyway).
As a kid in the 80s, I always thought it made sense that phasers could be fired from aft and not forward when at warp. That way, a pursuing ship would simply ram into phaser energy, as opposed to the phasers running into something.
IIRC, didn't the E-D fire aft phasers at warp at some point?