Reviving already takes energy, so let's figure this in terms of CE, shall we? I usually don't seriously consider NOT reviving until the cost gets up to 20 or 40, since I'm a free player; for nasty endgame content, though, we're probably looking at about 80 to 160. Since using this will probably save you around 100 energy or so, so it should be priced at about the same level at 100 energy...
See where this is going? Why wouldn't I just buy energy, which I can do from anywhere, even when I'm dead?
Makes sense to me.