It just came to my mind andit would possibly be op as ■■■■.
Make rune of justice work like homing arrow but with holy property missiles.
Skill level increases amount of missiles. Could be 5*Skill level. Each missile doing no more than 100% MATK.
Level 5 would be 25 missiles that could all focus 1 boss or spread targets. Divine might would be a great boost to it.
In game animation would need to change to a shitton of missiles popping out of the rune towards the targets in a very fast succession.
I find it a cool idea that would give Rune Caster somewhat better single target DPS than it has right now without having to go foken cryokino.