The text says Barbarian's (primal) powers should be called "rages", while they are referred as Evocations in the power writeups?
Copy-n-paste errata?
Anyway, interesting gimmick of primal power source. Powers last the whole round (or until you use another "rage"), so you have a default feature that lets you "burn" leftover powers for a level to damage conversion.
Have to see how it works,