Having heal in rankeds its just a waste of a Summoner Spell, if you're in ranked, your AD carry should be not retarded (As well as theirs) To focus on killing when the laning phase is for farming, you shouldn't have any problem with healing until you get to lvl 6.
Also, you should choose a right support for your carry, ie: Sivir and mana whores champs should be carrying with a Soraka (Sivir, Tristana, Ezreal, Urgot etc) Champs that conserve well without any mana regen help and that needs a lot of heals should be carrying a Sona (The most clear example is Teemo), and champs that can be devastating early game, ie: Vayne, Graves, Ashe etc should be carrying a janna for a total lane dominance.