Regardless of how "homogeneous" or not you think the healers are currently, taking an ability one of them has and giving it to the others is a definite step towards making them more homogenous.

(Also, I've always figured that SGE has Icarus because it's the only healer whose AoE heals are always centered on itself [versus Cure III, Asylum, Earthly Star, Sacred Soil, fairy].)