Honestly, most of the healers are quite good. I use Jean on my main team and Barbara on my second and both are great. I don't really use him, but Bennet is arguably the best healer in the game. Shinobu seems to be really solid too. From what I can tell, Diona and Sayu are both solid as well. The only healer who isn't very good at healing is Noelle and she's got shields to make up for it.