probably due to the future of light selection... plus Sol is a thing and covers any healing on her own if done right... (and atum is the only auto-revive we got right now)
but dark does have a decent comp. i've even pulled the right hime so i can hit the def debuff cap. even got chernabog on top of that and she's a total badass.
osiris is pretty much their only non-limited SSR healer (as of right now as far as I know), but dark can definitely break out both debuffs and damage (and some kami got some sort of sustain like self heals and such).
even then though, to break out the most of mana and anu (and eventually other elements when their 120% eidolons hit), gonna need to save up matching element eidolons or you're locked at roughly 80% (100% for the future 120% ones)