"You know what? For boss fights, I'm just not going to give a smurf about rank. I got 3 stars against this big dude in this next timeline - Aloeidai is its name apparently - and I am perfectly satisfied with my performance. For my monster in this fight I brought along the crazy wing dudes you find who are Synergists. I figured some buffing be good. Right now, Noel's only Synergist abilities are Protect so I figured Bravery and Faith would be great here. Sure my monster died about 1/2 or 3/4 through the fight but we did perfect as far as I'm concerned."
Spoiler: A decent performance is actually what gives you a 3 our of 5.