In every game I've played (I only play solo/AI), I've found that nearly always, building the planetary bombardment ships (for whichever faction), turns out always to be nothing but a waste of time money and resources. when part of my fleet, these ships are always the first to be targetted and destroyed, and never last long enough in battle (much too lightly armoured) to be worth almost any effort in building them. Thus, I've never destroyed a planet until after all other defenses and other ships around a planet have been destroyed, and since the bombers are all dead, it's always the capital ships that do the final cleanup of destroying the planet.
So, am I doing something fundamentally wrong in using them? Or are they just wasted effort?
I'd love to see updates/upgrades specific to these ships to give them more armor and staying power, or even the addition of a later-game "big bomber" with more punch and staying power.