Whirlwind is for mobility and healing (as you guessed). The most dangerous circumstances in this game are getting trapped by enemies or in ground effects. I simply won’t play a barbarian without it. And it spends fast enough, while moving. It’s actually on my left-click.
So, between the changes yesterday, and rolling all resist on my helm, and switching resist to physical on bracers, I’ve gone from struggling with 8s to breezing through 9+ (just ran a GR42). Elites and champs aren’t quite dead before I can finish leaping, but it’s nice to actually have a reason to use seismic slam.