In FC, SF using only known-to-borg, previously adapted-to weaponary (like the phasers you say are useless, even though they always work once or twice), were able to kick the **** out of the cube. This is in the movie. It means the borg adaptive shield cannot sustain that kind of bombardment. We see phasers and torps blow big holes in the cube, we hear reports of serious damage, and they dig a fricking hole to China in the side. Are phasers still useless?
I don't understand this Superman attitude. Sure, a cube can shrug off E-D firepower or VOY firepower after adapting to the built-in weaknesses of phasers, but why assume it can resist a whole fleet? We have an answer, and the answer is 'no it can't'. Before anyone brings it up, Wolf 359 involved Mirandas, for chrissakes, and FC was after the Dominion war militarisation, so the fleet was obviously superior.
What about weapons without a coherent frequency? Like particle beams, nuclear weapons, biological weapons, etc? I assume the borg have 'regular' shields as opposed to the adaptive ones, but I've no idea how good they are. We know they don't handle physical impacts well, probably because of this lack of a frequency to adapt to. Of course, beam cannons, being (as far as I can tell) coherent beams of light, may have a coherent frequency, rendering them less useful vs the borg.