All you really need to know is that anything directly in front of you (given that they're on the same elevation as well) will get hit. That being said though, it's width is an absolute joke. It's no wider than a roegadyn even at lb2. Everyone in your party can see the blueline indicator, but honestly its so brief that it might as well not be there because you won't ever get anything into position.

And on a side note, it's pretty disappointing that ranged LB does less than a caster from what I've seen, considering that it's effective range is less than that in most given circumstances.