Leia is an RNG dependent character. Lando, QGJ, Rey, Wedge + Biggs (in concert only) are all good damage dealers.
Fives is good with a Rex lead, because he benefits more from the turn meter boost, but isn't necessarily the best. For what you have, he's good at the moment.
Healing was important pre-protection. Once protection came out, healing went by the way-side. You'll learn why as you level and gear and mod up -- 5 dot mods with a health primary ability give +5.88% health. 5 dot mods with a protection primary ability give +23.5% protection. Given that your tanks often have as much protection as health, if not more so, +23.5% is far superior to +5.88%. Since protection can't be healed, healing is not particularly useful once you get into g7+.