It's actually 1 rage per 3 seconds.
It is the first talent. At 20lvl in DPS gear you normally have around 1000 armor. You just wasted 3 talent points for 10 attack power. This talent is godawful for leveling and only becomes good if you're wearing full Plate armor (not before 45-50lvl), which is also "blue" and for your level (not before max level). Thunder Clap is only good if you're facing more than 1 enemy, and only so until you get Sweeping Strikes. Beyond that, you pretty much don't use it for its damage.
Why? You get 50% free crit on your Overpower, 25% on your first Mortal Strike from Juggernaut, and some 10-15% passive from gear. Why would you need more? Blood Frenzy, Trauma and Deep Wounds are already up from these, going for more crit than that is just gimping your damage output.
That's why you pick Second Wind deep down, and then go for Blood Craze in Fury. And First Aid. And Cooking. I've never in my >10 years of WoW leveled a Warrior without First Aid, and I've leveled dozens of Warriors.