During this first encounter with the Borg, Enterprise's phasers seemed to be very effective against the Borg cube. I can understand why Picard might opt not to continue firing once offensive action against Enterprise has ceased (tractor/slicing beams broken), but when it was clear that no amount of diplomacy or speed would stop the Borg aggressors, why did Picard not resume using phasers?
This early on, it did not appear that the Borg (individual drones on up) had the adaptive shielding we later see. It would be logical to, when the photon torpedos had no effect, attempt firing phasers, would it not?
Is there something that prevented Enterprise's phaser banks from functioning properly at high warp factors? Did the Captain and/or crew know something we viewers did not? Or was this just another cheap plot device?