Or am I missing something that results in it making sense? It's a bother having to approach the target to do this attack skill before running away to a safe distance again where healers belong. Using Phlegma would be great and not a chore, if it weren't hamstrung by this weird need to be right in front of the target next to the tank in order to use it. Also note that Icarus (gap closer) is not intended/designed to be used in conjunction with Phlegma (before that excuse comes up), although technically you can waste it on gap closing for Phlegma if you want (for style points at best).
Apart from that (and the silly decision to turn all sage skills blue as you level up), Sage is great.