The only problem with Rage-Strike is it's presentation. It's the first power in the article, so it's the first thing people look at and try to grok. People look at it and go, "THIS IS THE MAIN DAMAGE DEALING MECHANIC!" when it's not. It's just a way for a barbarian to use mutliple dailies (LIKE EVERY OTHER CLASS CAN) without being penalized.
You get into a fight with the big baddie. You blast off a daily with the bonus you want for this fight. However, the fight turns south, and you are going to need to use some more dailies. Every other class in the game can go ahead and dip into that second daily. Your barb on the other hand would lose his current bonus. So instead, you can not just use that second daily for an attack without losing your bonus.
It's a pretty simple mechanic. Without it, you are discouraged from using multiple dailies. With it, you are now balanced with every other class in daily using.
I think if it wasn't the first thing people read and try to absorb, it wouldn't be causing a problem. It's NOT the main damage dealing mechanic, so don't worry about it.