The build is simple enough. You activate Battle Fury to get 15 rage from crits, then you spam Sprint, each time the whirlwinds crit you get 15 fury which you dump using Seismic Slam while the rapid fury gain extends the duration of Berserk.
The build has two main problems.
1) The damage output isn't great, almost all your damage comes from the Sprint whirlwinds. Elites take forever to die.
2) While Berserk makes you immune to all CC, it doesn't do anything about Waller.
I'd probably use a build slightly different from the video:
Mainly removing Bash since there's no need for it, replacing it with Furious Charge, that way you have a method of escape when walled/vortexed/whatever.