Juno's fine, it's just her skill is frequently unused in situations since it's antithetical with what a healer is usually used for. I use her as my third healer after Black Iris and Saria when I need one.
JustAPasserby: 'Red arrow thingy' means a class changed unit. You've already done that with several fundamental units which means you're well on your way already. Continue leveling those units while leveling up others for class change. Another healer(Iris, since she's so close anyway), another archer(Spica from the trading post when she's back) and another witch are decent bets at the moment.
You have some pretty nice plats - Lyla/Laila, Marle, Flamel and Shizuka especially. I'd level those too.