The only limiting factor of WW is damage. DHs, WDs and Monks deal so much more damage than me. You really need to stack Attack Speed to make the tornadoes do the heavy lifting. Pain Enhancer helps a lot. There's also Threatening Shout - Demoralize to group monsters together so that your tornadoes won't spin in random directions dealing no damage.
Clearing the actual rift is incredibly fast with ww barb..
I'm having a similar problem trying to hit the high GRs with WW barb. I'm about to switch to HoTA build though since I've got ancient IK pieces instead of my crappy normal Wastes.
Solo hota is not something I would recommend. WW or Rend really.