Noone really knows how, not even if it’s giving too much or too little rage. Blizzard noted that “Endless Rage is not granting the correct bonus to rage generation”, it’s been on since patch 2.3.3. When I first read that note, the first thing that came to my head was that my beer is just about to end and I need to grab another one, the second thing that came to my head was:
 

/care

 
Yea, that’s pretty much all I’ve to say on the topic :P.

Terhix