I use my Berserker set but not often and only in game stages. The problem is the options. If you can see the stats of a berserker and compare it with other unique swords like inferno, lightning or dark, they have 8 options versus the berserker and blizzard with 7 options. What's more the value of stats differ because they have higher stats (400 max) than berserker and blizzard (300 max). Also the Critical hits and attack speeds are better which is why most people prefer those 3 level 50 equip items. Although Berserker set has excellent set effect, other people may see it insufficient just like a legendary sword when using it in arena where better stats matter.