First off, the warrior in that video is absolute garbage. He is wasting cooldowns hitting absolutely nothing, and not even doing what he should be doing. His auto attacks alone are so disruptive that a berserker just can't do anything against them. I've won against almost every berserker I've dueled because of how laughable it is to actually fight them if you're any good at the class. Berserkers are not scary at all 1v1.