It’s an idiom that means “it would be reasonable”. Please don’t take that literally or personally.
I understand that sentiment, I just don’t see how it’s practical or realistic without removing AOE/high cleave weapons entirely. They will inherently get better with higher density of enemies. What’s your counter suggestion here?
You’re getting “viable” confused with “competitive”. I’ve solo’d Legend numerous times with Blumtsman, it still performs very well on Legend, it just doesn’t shine to the extent it does on Cata and modded. Bluntsman as a build does not get less viable as you go down difficulties unless your definition of viable is actually to get the most green circles. It’s “mediocre” (AKA fine, just not exceptional) on Legend because you rarely get enough density for it to hit cleave limit, that is to say it’s overkill so you won’t see its maximum performance. Still a damn good build.