With Magic and Range, the only ones who actually see the visual are the other players. It's mainly a notifier to let the tank know not to move the mobs from the location.
Well, with the caster LB at least, you have to pick the area it hits yourself (which is also a great boon that healer LB3 does not have), and you get to see the range it'll hit there, so that's not really an issue.

This wouldn't work for Healer LB3 because it's pretty much an instant cast that activates around you. So there is no need to show a visual to something that occurs in a split second.
Even if it was there for a split second, it would still help to teach players that "hey, the range on this isn't unlimited, maybe I should pay more attention to my positioning when I use it"

That or they could just read the tooltip, but who does that? Moreover, it saying it has a 30y range doesn't necessarily give healers a good indication as to just how wide that is. I don't think healers even have any 30y range spells to practice with, and you can't practice with LBs when playing solo, obviously.

But that's why I think they should just up the range on healer LB, preferably to match the range of tank LB, but even something like 40y would be okay too.