I haven't gone through the logs yet, but I do know he calls 2 berserker's to come help him. I mezed with my bard and they strolled away after mez broke. These berserker's we're already spawned. He didn't summon new ones. They are not leashed to him once he calls them. And I am guessing if you have all the berserker's dead there will be none to come help him.
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For once maybe someone would call me "sir", without adding, "you're making a scene"