Soraka doesn't help to burst down, she helps to out last the opponent.
For example: Soraka and Corki vs Janna + Anyone
You exchange evenly and when they go back they buy potions and you don't. You are auto winning on gold just because you don't have to buy the potions because Soraka heals so much.
Soraka/Corki, imo, is top tier because of that.
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The Cult of Personality.