The staff requires level 50 to be equipped and has no class restrictions, although its passive ability only works for feral Druids. The Ancient Divining Rod is a Phase 3 BiS item for Feral Druid ...

You can continue fighting Bristleback Shaman but you could also get nature damage by dueling a Shaman with Lightning Bolt and Earth Shock or a Druid with Wrath. After having taken nature damage 10 ...