Fan of Knives gets MUCH stronger when you take the passive skill at high level that passively adds crit while out of combat, meaning you can push it to double effectiveness, making it all the more rapely. At that point, you can either add double range, for more hits, or you can add stun. Either one is viable at the lower levels. The reason the Crit Bomber spec goes for the extra range is to take advantage of that guaranteed crit, to get it out on as many things at once as possible. It won't one-shot things at max difficulty by any means, but pushing your damage to maximum effectiveness is a requirement for the Hell and Inferno modes, since killing things as quickly as possible becomes a much more important priority on those difficulties.
Also I gave it the name Crit Bomber because at the time I was thinking of it, it reminded me of Reckoning Bombs from WoW, which were also reliant on critical hits, though in a different way (getting critically hit versus putting out crits.)
By a similar reasoning, crit bomb Loaded for Bear Cluster arrow is gonna be your bread and butter attack for Elite groups.