is there any way to nerf soraka or that keystone?

Many champions can be annoying to play against. That does not necessarily mean that they are overpowered.

I'm not supporting or defending Soraka, but you should probably come up with a better argument than "I don't like playing against her" if you intend to actually have a discussion.

working hard and risking your life to lower their adc's hp, only to have soraka easily heal the entirety of their hp back in a few seconds is pretty cancerous.