Even a pack of rats can bring down a magnificent Lion if there's enough of them.
No, I disagree. Transport ships have very little in the way of armor or weapons. Also, slower. Any cruiser should have a field day against them. Programmers are taking the easy route and simply assigning combat power to units regardless of reality. IF you move transports and you don't want them sunk, you should have to also assign combat vessels to escort. This part oft he game is too simplistic and unrealistic.