Berserk has a pacification because the name of the ability is "Berserk". You go nuts, then you need to calm down and take a breather. Not everything is solely based around your rotation or an ability's effectiveness in combat.

Also, while pacified you can do Brutal Swing -> Flash x2 and you'll be back in play. You can also pop Vengeance between Flashes.

Also also, the pacification debuff can be removed by a healer. So you can macro it to say when your Berserk ends and when you need to be Esuna/Leech'd.

Also also also alsoalsoaososo, you can couple Berserk with Unchained and Internal Release at the start of the fight and get a huuuuuuuuge lead in enmity.