The flipside of a daily rage is in one-encounter days, when the huge benefit of the rage is essentially an "at-will". And the barbarian with a daily, powerful rage has a bazooka: if the encounter is just average in difficulty, he either overkills by spending his biggest resource (without knowing if he'll need it again) or doesn't spend it and is left feeling like he's not really a barbarian.
One way to address both sides of the rage coin: have more granularity in the rage. Instead of "rage" being a barbarian ability, it becomes "rages", a type of barbarian ability:
- Raging Strike: the reckless, "I dare you to attack me" attack where the barbarian throws caution to the wind.
- Battle Frenzy: the "must keep attacking to maintain it" rage, with moderate benefits. By its very nature, won't last an entire fight, but ends at the end of a fight.
- Raging Trance: the "daily" rage, where the barbarian surrenders his body to a deeper, instinctive level of being. This one has the huge benefits.