If you have maximum fury, SPEND, SPEND, SPEND! This comes down to the mechanics of WoTB, if you gain 25 fury whilst at maximum, it wont count towards your refreshing of WoTB. In order to keep WoTB up, you have to constantly have room for fury to be added and therefore refresh it. I personally use Rend for small spends of Fury, and Battle Rage and Sprint when I am gaining fury rapidly, ensuring that I am always at less than maximum.
Elite packs can easily refresh your WoTB. If you can circle them in a tight space, or even just two of them, then spam your Battle Rage and Sprint buttons and your WoTB will refresh in no time.
Rare packs. You only need to kill one mob here to get the NV stack and the loot. Sure the individual mobs have a chance of dropping rares, and even legendaries, but the time it takes to kill them can easily outweigh the chances of getting whichever item you are hunting from the next elite/rare pack with your new NV stack. Take down the yellow circled rare and ignore the other mobs and move on.
Not all shrines are good shrines. The essence of WW Barb efficiency is to have your WoTB up all the time, or at least as much as possible. That is why I do not ever click on Empowering Shrines. Sure you get more resource income, and faster cool-downs on WoTB and all other spells, but at what cost? If I have clicked on an empowered shrine, and hit something, I get a bunch of Fury from the hit, some for having a mighty weapon, and some for using Bash with the Extra fury skill. I also get a bunch of fury for having clicked the empowered shrine. This fury DOES NOT go towards refreshing WoTB. That means that its getting you to Max Fury much faster, and keeping you there longer, greatly reducing your ability to keep WoTB refreshed. I find that unless I am constantly spamming all fury spenders, I cannot keep WoTB up under their influence. You cannot unclick an Empowerment shrine either.