Superbolide is a better Invuln to use early than Living Dead, for certain. I do try to limit how much I use it with SGE/SCHs at least, but timing it around when you know a WHM has Benediction or an AST has ED up saves a CD use for the next pack at minimal cost to the healer.
Do I think it's an "on CD" use like Holmgang or HG are? Not at all. But saving it as an emergency button is also a bit of a waste, too. Of course, like many things, it depends heavily on how your party is doing overall and especially requires both healer and tank to be paying attention. I know if I ever get a GNB when I'm on healer, I tend to conserve Benediction (or SGE's quick heals) more than I normally would just in case. It's just an invuln that requires more situational awareness than some others do.
Still better than Living Dead, though. And a heck of a lot less confusing for people unfamiliar with how LD works.