WotB is impossible to keep up unless you play really high MP or your dps is low and high crit chance. This is because they nerfed the proc rate of nado ticking into the fray from 0.2 to 0.08 in like 1.06 to 1.07 (I think then.) There is no other better skill as it pops WotB on for hard elites only (if it doesn't, change that setting) and probably keeps you from more deaths. It's basically the best speed steroid in the game.
My suggestion is as long as you're sprinting everywhere, you're doing okay. My bots never keep WotB up all the time, it's not a problem. If you really want longer WotB try geting bash - instigation as your main attack and switch superstition to bloodlust.
This nails it. Other advices to raise your wotb uptime:
go 1 or 2 mp levels up. You need thrash mobs to NOT die from 1 ww, but to die to the Run like the wind hurricanes. There is a huge difference between mp7 and mp8 for me in wotb uptime.
If you are not using scoundrel, get it on. Put a buriza with 13+ freeze % and a freeze chance % amulet on him. The added crit and the continous freezing help a lot, you need to try it in order to believe the diference.It will also make you feel you are playing at a lower mp in monster damage.
There is an optimized barbarian.cs somewhere in rixx act 3 thread. It will use the fury generating and spending skills better, you'll need to download it and replace the old barbarian.cs at C:\Users\XXXX\Desktop\Demonbuddy\plugins\GilesTrinity\Abilities.
Last, the most important aspect is the profile. Some very good profiles like rixx are not especially good for Wotb barb. The one that gave me the highest uptime and the best results was Ultima magi, you should try several to find the one that suits you.
EDIT: If you are doing mp10 rend is fine; if lower mp is your preference, I'd switch rend for overpower, the added crit rune. In fact given your wotb issue, I'd change it anyway, added crit will always help.