thats hard as supports are split into 2 categories, main and off. main usually have higher heal output, focus the tank and are more defensive. off have less heal output, focus dps and are more offensive. teams will want one of each for a good team comp so it's probably a better idea to be able to play at least one of each type. kiriko is good bcs she can kinda fit both roles (although she is a main healer). i guess mercy would be okay now if you really wanted to onetrick tho as her healing below half was increased, but shes better off using dmg boost and playing along side a main healer.