Um...What's the point of this discussion about the NPC, really?! In this game gladiator NPC's can heal. An ex-warrior NPC at lvl60 heals for ~10000HP with a spell that I don't recall seeing. Black mages use spells not available to players. Same with just about any other class.

Don't base anything on NPC's and their skill sets. Yes, the LORE suggests that if they will come, they're more likely to come as healers. Frankly I hope not...at least not in 5.0 seeing as I want a dancer and for it to be a healer and I doubt we'd get two healers...but hey.

By the way, Black Magic and White Magic have the same origin as far as I remember the lore related to them. Black magic as it is was simply formed when Shantotto decided that she's not happy with just her own aether cause it limits how much boom and blast she can do so she invented a way to draw in outside aether. That's all. There is no reason to assume that there are no branches of geomancers that are basically any of the three roles. Ones focused on destroying evil (DPS), ones on wards (tanks) and ones on restoring damage caused by evil (healers). The NPC's grandfather (or was it father?!) could have been the "wards" type, seeing as he made a ward powerful enough to hold the beast for so long without sacrificing anyone's life.