Endgame sets need to be class specific, That meaning- Dex=birds. Int=Mages. Bear=str. Rhino=Str. Fox=Dex.
This doesn't mean those players can't add dex/int or str to there build. They just can't use a set that's not meant for there toon. This would end the pop balancing issues for the most part. Most classes seem to hold there own quite well when they are played by a skilled person.