Hehe, yeah, but that's sort of the point... and the sentiment behind the "Sweet fortune, what a jump!" comment. But in theory, you should be able to blitz the beams and rescue the cruisers (or at least you used to be able to). Now though, they soak up too much damage to kill quickly, intercept 50-75% of incoming Paveways, and fire non-stop, killing the cruisers in a matter of seconds.
I understand that originally it was awfully easy to save them (provided you were ready for the Medea), but good grief, feels like the difficulty of keeping them alive has maybe been overdone a bit.
On another note:
During Darkest Hour, some of the warship behavior seems a little... lacking in tactics.
When the Indus jumps in to bring down the Valerie, it generally cripples her engines right off the bat, leaving her stuck in place and unable to reposition herself. And while I understand that it's maybe a bit much to ask of the AI to respond dynamically to an enemy warship's condition, it does seem like Captain Sorenson makes a pretty odd decision: Rather than hang out behind the Valerie and pounding it with Mass Drivers as well as torpedos, or at least attempting to drop underneath the Valerie to get into her blind spot where her slash beams can't hit, the Indus moves into broadside position opposite the Vatican, so that the Valerie can easily bring all 4 of it's beams (well, it would if I didn't disarm it at least) to bear on the Fed's ships. Seems to me that it's kinda silly to purposefully position yourself so as to bear the full brunt of your enemy's strongest fire concentration. It would maybe make sense if the Indus moved to the Valerie's port-side to position herself between the corvette and Rheza, but instead the Indus moves to her starboard, between the Valerie and... nothing.
I guess it also seems strange to me that once the Valerie realizes it's toast, it doesn't attempt to knock out Rheza station and at least complete its mission objective before going down... Or that the Atreus doesn't at least try to take a potshot at Rheza (or one of the Fed warships) after taking down the other station, and instead just sits there taking fire from the Vikrant and Torreador before leaving.