The goal being to maximize rage gernearation for active use mitigation / self healing. Sources I've read even prioritize Crit/Exp over agility on gemming.
Ideally you'll have enough rage generation to use all savage defense charges and have additional for frenzied regen and empowered maul. This priority also gives you enough rage to feel like its a more active playstyle and not just stacking avoidance and hoping for the best while wishing for more rage.
Bears feel like they're in a very good place right now. Despite thoroughly enjoying Moonkin I'm happy I traded feathers for fur a week or so ago. -- Eumaeus, Guardian/Balance Druid GM - Lux ex Tenebris - Sargeras | Alliance [6/6] MSV [2/6] HoF