It is what I observed. I'm not sure which tech exactly, or if it required all your techs to govern it as it is tricky to determine what level your opponent has.
But my observation was from having opponent empires start at different tech levels while I played the Romulans. When I invaded the Federation systems who were level 8 my Battlecruiser 1s would be destroyed. Battlecruiser 2's have shield+hull of 650, thus they were doing 640 damage (+80 antiship times Tech

. They would have 10 hull, but their shield completely restored as battle was over.
The other part was that Orbital Batteries and invading ships lined up with each other with each Battery shooting at only one ship. Thus it was necessary to have as many warships as their were Batteries to soak up this damage while the Transports went by.
I'm not sure in turn what your ships targeted, but if there were Planetary Shields those tended to get high (but not guaranteed) priority as they completely blocked Transports.
As you can see, the early ships would get creamed by Batteries, but as Tech goes up ships outstrip the damage. You will also note that the high end Command ships were better than strike cruisers.