Here's a replay of a friend and me getting 4 stars with a random team and earning us the Shield award. https://wowreplays.com/Replay/38925
I'm calling bull on the fact that we didn't get 5 stars despite killing the last ship 4s before the main wave started. Guessing this is a bug that needs to be fixed?
As for my personal experience, Ryujo is good if you do manage to clear all objectives as this ensures the Koku CV doesn't spawn (her fighters will kick your arse), if you fail to defend the perimeter then an Independence should be able to keep the sky clean, I'm no example of that in the replay as I was fully stock at the time.
Oh and my friend was forcibly disconnected from the game when he was going after the Koku, nice scripts the game has there, seeing as his Internet was working perfectly fine at the time, luckily enough he managed to get back in and succeed in his valiant attempt.