My idea is that you keep the attacks that use rage, spend rage, and do neither just the way they are, but you generate rage in two other ways as well. One would be similar to Berserker Stance, you generate 1 rage from each % of damage you take. The second would be similar to Defensive Stance, where you generate rage passively while in combat at a slow rate. I am unsure what the amount of rage generated passively and the rage generated from taking damage should be to be balanced.
The stances would change to be amplified versions of these passives. These changes to stances are only from a rage generation perspective, so any other effects would remain. For example, if the rage you generated from taking damage was 1 rage per 2% damage taken, it would change to 1 rage for every one 1% by going into Berserker Stance. Let me know what you think, and feel free to modify this all you want, just wanted to get my idea out there.