A moot point though, as a fully-crewed Enterprise would have been able to raise shields and simply blown the Bird of Prey into scrap anyway.
That's what Starfleet wants you to believe. Exactly that should have happened in Generations. And that was a Galaxy-class, no less.
Grissom took one shot to destroy and the Klingons weren't even wanting to blow it up. Valkris ship too. The Enterprise hit the Klingon ship with two torpedoes, the same amount of firepower that tore Reliant in two, and only barely scratched the paint (ok, they killed the dog too).
Birds of Prey are fucking dangerous.
Kruge was a complete whacko
That he was.
That's the problem as the writers keep "adjusting the tech to fit the plot".
Sometimes, a ship will take a severe pounding and hold together, like the Enterprise
in Undiscovered Country, the Enterprise-D
in Generations and the Odyssey
in DS9 - okay, the latter two were destroyed, but they spent the entire engagements effectively unshielded. As you said, Reliant
only took two photons and was completely wrecked.