I've always felt Picard's battle orders in that scene were very lackadaisically given, like it wasn't that big of a fight. This heading & that heading & dispersal patterns instead of "fire everything!"
We have to consider that Picard did not want to win. He had a specific tactical goal in that battle, and it had nothing to do with destroying Klingon ships or ensuring the survival of the E-D. All that mattered was getting the E-C safely back into the timehole.
I can buy extremely restrained fire, then: Picard would have to goad the Klingons into attacking his own ship and ignoring the E-C, while making sure the Klingons did not realize they were being goaded.
Indeed, I wouldn't have been surprised if Picard had used surrender as one of his tactical maneuvers here; it might have been among the most effective in securing victory for his side. But apparently this war-hardened version of the Captain was blind to such an option.