EE the best all way ... his heal removes all negative status effects before it heals (=heal immunity is gone) and has the chance to revive a fallen char, plus he has a extra revive ability (which is not based on a chance), plus he has the chance to gain a lot of tm, plus he grants tm on basic. He also has a not too low amount of hp, protection and defense, what reduces the chance of getting 1-hit-killed.
Just in order to "heal", i would also note Barriss Offee ... her leader ability heal is a free heal every single turn without the need to use an ability and adds max health in addition. her special equalize hp, so chars having low hp + heal immunity still come out with a higher hp. Barriss HP and Protection is nice so she for sure wont get killed in 1 hit. Her weak points are speed and attack power ... she is very slow and does almost no damage. her tm-gain from allies getting crits would need a buff to make her more useful. but any way, she was GW-Goddess for a long time.