I understand what Blizzard is trying to do. They're trying to make sure that we don't 'waste' rage after hitting the maximum 100%.
Why not just keep it simple and make inner rage an out right damage attack that saps some rage when you hit 100% rage.
Something like "When the Warrior reaches 100 rage they explode with fury causing X damage and consuming Y rage"
X damage would be something not too hard hitting, but still worth the rage cost. Something like talented execute damage (maybe a little more, like 120% execute damage) for 30 or so rage. And give it like a 10s or 15s internal cooldown so it doesn't get abused.