Right. Berserk is basically only cast upon your team for the sole purpose of hindering your chances for winning the fight. Take Spectral Keeper for instance; it casts berserk on your team in order for you to attack it immediately so that it can pull off a mean counter-attack on three members of your team. Or a Malboro; it casts berserk along with darkness, poison, and confusion so that you'll keep attacking but at the same time, you'll keep missing so that you'll eventually die of poison.

The only being that berserk really aids is the Wendigo that you fight by the Macalainia Temple.