I could see it get a +1 mana cost maybe, it's currently extremely efficient for healing, especially for being neutral and a mech condition activator(not necessarily useful in every deck but still). It's basically Far Seer + Holy Light for one card(slightly less than that but still). Mostly the broken aspect is the neutral, it's like not that good compared to paladin/druid typical heal choices(and warrior armor), but for everyone else who didn't have any heals, it's way good, and it's a lot more usable than Alexstraza(both in cost and in the way it's used to recover health since alex only works when you're a good bit under 15, though obviously it has other uses also). And when you give decks that typically traded health to do stuff like rogue or handlock a very good heal source, well that becomes kinda mandatory. It's also used in mech decks just by nature of being a mech and easily replaces frost armor secret for mages in that regard.