Originally Posted by L0cke89
Just to keep you from getting more frustrated.
PLAY ON HARD. It brings you nothing to do on normal since you won't get the overall A-Rank.
Did you make sure not to many buildings got destroyed during the Tempest fight? I would say more than one, try again. Two or three should be fine but it makes the thing REALLY hard.
To check after the fight just leave the area and save on a different file. Go back and check how many buildings are damaged. The save is so the enemies won't damage any more buildings while you're looking around.
For the mission itself I can't give any more help than the above mentoined route I take. But a little bit of luck is involved, because the AI changes behaviour sometimes.
You have a good point about the Tempest fight. Could be it.