Mafia: general discussions.

Percentage-based defense doesn't make Berserkers overpowered. But full defense does, because usually, everyone delays casting spells on them, prioritizing casting spells on other units, and then it's too late to remove the defense.

And it's even more worthwhile to leave such defense on a Berserker, because what if their only defense is broken early on, and even if it's just by chance. Then someone else will finish them off, so it doesn't necessarily depend on the player's skill; they might be killed for various reasons. And this randomness can help the Berserker survive until the end.