Well, moving damage from tornadoes to WW itself is definitely an improvement since Wastes was already awesome in AoE clearing but suffered quite a lot on Guardians and beefy elites. This swap will make the second much more bearable and i suppose we will see an improvement on clearing times.
Anyway, it all depends on what you consider "viable". Basically any build is capable of compelting the journey with not many issue apart maybe certain Set Dungeons or Conquests (still doable, but some are definitely harder than others) so if your goal is the Guardian, you'll be fine.
If your goal are ladders, you shouldn't care about a certain set being viable, but only about the best build for pushing.
before the buffs it was sort of on par with old ww, falling behind a bit in extremely high density maps where the tornadoes shined more, now after the buff its pretty much the top solo build, with multiple gr 90 clears already right after the leaderboards reset on ptr, we'll see how it stands after a few more days of testing