[Maltrease]

I haven't played with Ko-Oni so I can't comment on the "balance" side of things. However, I really liked Kristoffer's comment about making the Oni retreat when in ghost form and making them more difficult to banish in ghost form.

"We have driven the demons back today... but they will return soon."

So in a sense you have all these priest which are able to easily temporarly banish the demon army and drive them off the battle field but to actual "kill" them takes a lot more effort. That sounds really fun and full of flavor to me and invites specific strategies to actually kill the oni ghost instead of automatically having the priest do both jobs.

It also sounds interesting that in ghost form all the oni want to flee, since of course they don't want to be permantly killed and now they are are at their vulnerable stage.