The only thing I could think of was that maybe, in STVI continuity at least, shields only defended against energy weapons, so Chang intended to cripple the ship with torpedoes and then finish them off with disruptors. Of course, I would expect a photon torpedo to be more powerful than what was depicted in the movie - the Enterprise was able to sustain about half a dozen hits and still remain operational.me,myself and I wrote:"She's packing quite a wallop!" <-- The only explanation we ever got.
Hmm, that could work. It would be consistent with Spock's statement that "the hull has been compromised".Captain Seafort wrote:Simple - they were hitting hull-hugging shields, not the hull. Note that through most of the battle only superficial external damage was visible, and it was only after Scotty's warning that the shields were collapsing that serious structural damage occured - the torp that punched a hole through the saucer.