I've never liked having a support Soraka.
The reason being is you have no lane pressure with a Soraka. As an adc you have to harrass and last hit rather than relying on your support to focus on harass and zoning. With soraka you do the bulk of the work, with her topping you off to let you do so. That is just so radically different than all the other supports that it just feels strange.
Yes her skills have changed and her silence field is nice, but a thresh or nami or braum or even blitz support can provide so much more pressure in lane, as well as usefulness when ganked or when in a simple 2v2.