Felajm berserkers were not actually common until the war with Gobnar broke lose. The berserker class was originally only used by Gobnar at the beginning of their conflict. The only reason Gobnar ever used this tactic to begin with was that their race reverted to barbarism after their change in politics and leadership. Gobnar were always more numerous and their leaders valued their lives less.

Jumping head on into the fight and swiping weapons all around themselves was not the style of Felajm warriors. The Felajm race was always rather artistic, ordered, calculative and precise. But seeing how surprise Gobnar raids kept decimating their villages and towns, the angry Felajm who lost everything they cared for became the berserkers. Felajm basically observed the behavior of Gobnar forces on the field and used the latter's own style against them.
This tactic prove to be exceptionally effective. Only few Felajm berserkers were able to decimate entire squads of Gobnar Raiders. Felajm, by being somewhat stronger and more agile, actually prove to be more effective berserkers than Gobnar ever were.