about the only issue o have with the capital ships of The Expanse is the huge blind spot the Drive section has for the CIWS grid. I would bulk up the centre section as a gravity ring and put the PDC around the ring to provide full 360 coverage.
Wouldn't matter. The Donnager wasn't destroyed by overwhelming fire. It was the breaching teams that managed to get to the bridge door and ultimately forced the Captain's hand to activate the self-destruct.
And the Agatha King was destroyed in a similar fashion. In fact I can't think of any capital ship that was destroyed with overwhelming fire and poor PDC capability. It's all been frigates and the like...
In the Donnie's defence for such a 'blind spot', her missiles have always been sufficient in preventing anything getting close enough for the PDC and rail guns to actually be needed. If it takes an exception to prove more than a match for Mars' greatest warship, then I would say such systems and design criteria are unnecessary, seeing as it was a secret weapon that proved to be its downfall.
And if we were to try and modify design to account for every possible contingency then we will unwittingly open the platform up for some other weakness. I mean that's like putting armour on the wings and chassis of the spitfire, whereas the fact that the plane could return to base with said damage and not perish is more important.
And it follows that the engines, for all their need in Zero-G, are nothing compared to the missiles, tracking systems, rail guns and PDC. And the conspirators knew this. Hence why this was no shooting battle. It was always a suicide run. The Donnie had to die, and the survivors of the Canterbury with it, whether by their hands or the crews...
No one expected the Roci to spring to the rescue!