Currently I think angelic is to good and is a must pick. IUNE biggest strength is that she can heal allies out of a wounded state, so keeping the cool down low on her heal makes her very strong. I also use stoicism, with this card plus her ability to gain an ally makes her hard to kill, if you stay close to your team and created ally. IUNE is very good as a raider, and breaks my personal rule of bringing only one alien on a mission because of what she can do for her team.
Now this is just me being crazy, but I have been testing out builds and strategies with IUNE as an antagonist. It goes about as well as I thought which is not that great, her weapons are strong and healing elites is useful; but, unlike the other characters she is very dependent on her cards to be viable. As an antagonist she either must go for a bust damage build or an elite heal build. With harmony and cautious she can quickly put raiders in a wounded state, but she relies on the NPC’s to confirm the kill. With abnegation and munificent she can keep elite NPC’s alive while using them as shields to avoid harm, the problem is that elites are not that hard to kill in the first place. But the biggest problem she has as the antagonist is that unlike the other cast she has no defensive options or ways to escape. Pulse she loses her ability to create an ally since there in nothing for her to turn in one (other than another IUNE created ally).
But she is my favorite character thus far in this game, and I absolutely would not change anything about her.