My personal feeling on this.
Too complicated, and exceptionally unsatisfying. The Rage mechanic is someone just getting WAY to clever.
The thematic feel of the Striker class is that it allows you to do X bonus damage, and gives you ways to enhance that mechanic.
This Barbarian right now, gives you your special. Once per day, that provides a minor enhancement for the rest of the encounter. And then as you go up in levels, you can dish out "Some damage" and then go on.
Right now, if I were rating this class, I would say it's a failure. Plain and simple. Go back figure out how to make Rages, provide different options to ALL attacks, (even if its only against one target, or some variable to that per round). And then let us try it.
Right now, this just comes across as way to clunky and not well done.
I don't like it and would not encourage someone to playtest this further. Cause as it stands, it's not friendly, or coherent. And I recognize it's a playtest class. And not fully finished. But they seemed to think this was a good direction and I feel in all honesty it's a gigantic miss.
Go back and find some mechanic that allows significant damage dealing, but in this case, change the mechanic to something that feels like one of the other strikers. Bonus damage, figure it out. But this way just feels wrong.