I take it you didn't actively play her ap mid (the reason she's being nerfed).
Ap mid you had to use starcall as harass which also pushes minions, it was great for harassing but when minions are pushed, you need to be near them for exp. Soraka lacks all types of escapes and there forth being on enemy side of river made you EASY prey for any good jungler as well as a good burst attack mid ap champion.
but it was fun. and it wasn't useless, so we did it some. And then Riot nerfed it some
Jungle shows up? No problem. Silence and walk away. If they somehow managed to get close to you, no problem, your heal is also providing you with a substantial armor buff.
Soraka was hardly a "high risk" mid lane. Mid lane is short enough that Soraka could just heal herself and walk out of most ganks.