Fight Song seems really strong as it allows you to reuse Tag Team multiple times in one battle while also giving MC a 1 turn assassin to go with it. In this battle, MC managed to use Tag Teams 3 times in 11 turns.
It's especially strong in Fire or Light I feel like because of their easy access to Double Strike to keep feeding MC with the stacks.
Should've ran Bubs main though to boost up MC's damage more.