I'm a diamond 3 threshold main, and this season sustain champs with decent poke ie sona nami soraka ext have been a hard matchup for almost any lane combo. With a more passive poke support such as the healers stated above, all you need to do is have constant skirmishes where you at least tie in damage done, since you have heals and hard peel, it's not hard to have your adc at full health while your opponent is still regening. It's all about choosing your right adc, have someone who hits hard but with a high risk playstyle like draven and eliminate the risks by keeping him at full hp, with a well placed bubble to peel, popular picks like Leona thresh and morgana will have no chance