COM, RAV, MED is generally the most suitable. In XIII I used to start the battles with SYN, SYN, COM for quick buffs or SYN, SAB, COM then I shift to COM, RAV, COM/RAV. I didn't like SYN in XIII-2 due to the lack of Haste, so it was mostly COM, RAV, COM/RAV there.
Actually I have two: Bully(Com/Sab/Syn) and Diversity. I used to start out with Evened Odds(Med/Sab/Syn) but that made battles longer. In XIII I used Bully with Light Vanille and Sazh. Then switched to Diversity
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