You might consider a variable effect based on the training of the mage that is the target of AJ. For example, Dark Mages -6 Life while Holy mages + 6 Life.
That sounds blatantly OP. The reason I came up with this idea was beause I was thinking of what it would be like if there was a card with a 100% stun chance, and how powerful that would be, and how that could be balanced. The idea of Asyra's judgement is that when used on yourself it increases your life by 6 (7 with Divine Reward) at the cost of stunning you, but that's not as much of an issue if you have enough action advantage. Or it can be used to stun the enemy mage at a crucial moment at the cost of giving them 6 life. 100% stun chance is very powerful, and to be able to use it whenever you want is very powerful, which is why I thought of the +6 life idea.
It can either help or hurt the target mage, depending on whether they're an ally or an enemy and when the spell is cast, even though the effect is exactly the same in all cases, the context would really matter. It seems to fit with the kind of poetic justice that I imagine that Asyra would be fond of, based on what we've seen of her characterization so far.