Still grinding in preparation for the Beast of Centaurea Ver.2 battle. During a practice run (I'm still about 30 levels below where I'd like to be), I made a few observations:
1. It's possible to win this fight very easily at my level with a particular strategy if I have the patience. Beast of Centuarea's normal form only has 24 PAR resistance, and is extremely slow. It's possible to have Suwako and Renko keep it PAR-locked for the entire fight with their extremely powerful PAR effects. If you can defeat the Beast of Centaurea's normal form before it uses Hahahaha! What's wrong?, then you'll never have to face the super-powerful Breakaway form. Unfortunately, this means doing an extra 100 million damage. However, since it's possible to PAR-lock the boss with some luck, I believe it's doable, if extremely tedious.
2. The normal form is susceptible to debuffs, but the Breakaway form is immune to everything. However, the Breakaway form still technically counts as an extension of the first form. That means it keeps any debuffs! Normally, Hahahaha! What's wrong? raises all its stats by 50%, which lets it murder you quickly with its fast attacks. However, by keeping the Beast of Centaurea at max debuffs before it transforms, you can nullify most of its buffs. Even better, it doesn't buff its speed when it transforms, so it'll still be suffering from -40% SPD when the Breakaway form is released, giving you a lot more time to prepare for its first wave. Sure, its spam attacks will quickly run down the debuffs, but it'll still make surviving its initial attacks much easier.