But the other strikers in the PHB have "extra damage" they can deal that do not expend any resources (Rogue's sneak attack, Ranger's Hunter's Quarry, and Warlock's curse), let alone cost that precious daily ability. If they wanted Barbarians to be a striker class, shouldn't they have a similiar mechanic? Perhaps there is an At-Will that I missed which generates the extra damage strikers are supposed to have.
But the other strikers in the PHB have "extra damage" they can deal that do not expend any resources (Rogue's sneak attack, Ranger's Hunter's Quarry, and Warlock's curse), let alone cost that precious daily ability. If they wanted Barbarians to be a striker class, shouldn't they have a similiar mechanic? Perhaps there is an At-Will that I missed which generates the extra damage strikers are supposed to have.
Rage
You fly into a furious rage, wreaking havoc upon your foes.
Encounter (Special) ✦ Primal, Rage
Special: You can use this power a number of times per day
equal to your Charisma modifier (minimum 1), but only once
per encounter.
Rage strike is not the barbarian's equivalent of sneak attack/hunter's quarry/warlock's curse. It's a way to let the barbarian spend multiple daily powers in one fight without hosing himself out of the Effect of his first rage power.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.