Factual error: The Excelsior detects the incoming shockwave from the exploded Klingon moon Praxis and is hit seconds later. Assuming that the Excelsior in these times isn't operating within Klingon borders (or even the Klingon solar system) and is monitoring the neutral zone light years away, the Excelsior cannot be hit or even be surprised by a shockwave coming from so far away. Gravitational shockwaves or explosions (even huge ones) are not faster than light. It would take years to reach the Excelsior.
GoekhanFactual error: When the crew member aboard the Excelsior detects the incoming shockwave, he states, "Energy wave at 240 degrees, mark 6, port". However, when the shockwave hits the Excelsior seconds later, it is coming from her starboard side. (00:04:05)
Chosen answer: There's a limit as to how much the shields can protect the ship. Depending on the force of the explosions, the ship still suffers some damage from any weapon blasts. Also, the shield only holds for so long and gradually loses it protectiveness with successive attacks, causing increasing damage to the ship.
raywest