This talent was changed in the 2.0 patch. Here are some numbers comparing the old and new versions for out of combat rage decay.

Pre-2.0: Increases the time taken for your rage to decay out of combat by 30%.
Given that you lose 3 rage per tick, and a tick is every 2 seconds, then over 10 seconds you will normally lose:
3*(10/2) = 15 rage per 10 secs.
Since the time take to decay is increased by 30%, you will actually lose this rage over 13 seconds, so :
Rage lost per second = 15/13 = 1.154

Post-2.0: Generates 1 rage every 3 seconds.
Considering rage decay out of combat over 6 seconds, you will lose
3*(6/2) = 9 rage per 6 secs.
However, in this time you will generate
1*(6/3) = 2 rage per 6 secs.
Thus, you've lost (9-2) = 7 rage in 6 seconds, giving :
Rage lost per second = 7/6 = 1.167