The katana still does decent single shot damage, but the chainsaw is better for long-term damage. Against scrakes and FPs, the chainsaw is your best bet, but on the lower tiered zeds the katana is a safer choice. I think the only reason that zerkers are not played nowadays is the fact that most other classes can take down everything at a safe range, whereas berserker can take down everything except FPs at close range only. Yes, pre-patch he was a beast and could kill pretty much everything. People fail to realize that you had to be in an enemy's attack range in order to attack him. If I'm going to be up in a gorefast's face, I'd better damn well be killing him faster than any other class. I think that in order to balance classes back out, they need to make zerkers able to decapitate the higher tiered zeds. That's all. Give us a chance (based on damage done) to decap an FP or scrake. It will assist the team in taking down the zed and also make it so our melees are actually worth the risk we take.
Every other class can use their primary weapons to take out any zed (barring medic, of course). I don't see why berserkers should be any different. Either that, or give us more damage resistance so that we can focus on being sponges instead of damage dealers. I'm fine with either role.