How is support Soraka

In lane, has the potential of frightening amounts of harass. Her E silences the opponent and costs no mana, enabling you to zone both carry and support from getting close to you. Combine this with and you'll be able to get near full-build by the end of the mid-game. Your heal and ult will always make trading difficult and the worldwide effect it has can save your allies, potentially turning the tide of more than your lane. If a magic damage jungler or your magic damage APC roams bot, spamming your Q will help them do more damage with the MR shred.

Her lack of hard CC does however make her lane extremely gankable, and all-ins from the enemy usually end with them on top, since your W has such a long cooldown. Your lack of outright burst or even substantial damage makes taking back a lost lane extremely difficult. Fortunately, it is easy to stay on top if you are careful and know what you're doing.

Honestly I never take support Soraka outside of duo's anymore. They get annoyed by me using my Q too much, they waste heals and don't use the armor buff, don't take advantage of her mana, or expect her to lock down kills in ways she simply can't.

I don't think she is bad by an means. I am on an 8 game winning streak as Soraka. But I would want the adc to be on the same page as me. Otherwise I would pick Nami, who is pretty safe all around.

I played her support, lost four times in a row.
Yep, nope, whatever. Friggidy-fraggedy-do.

I personally don't like her much because her support playstyle is far too passive. In terms of her viability, though, (as a S4 player) I think she's viable as long as your adc is good.

The problem with true supports at low ELO is that you're very dependent on your adc to know what they're doing, which is not a given.

It really depends on your play style. The meta shifts/favors supports with high CC and good engage. Soraka has decent poke and sustain. No hard CC however. She's kinda the opposite. If you're going to a farm lane, Soraka is not a bad pick. If you're headed into a kill/burst lane (Leona + Ezreal), you might not want to go Soraka. Since Sona's viability plummeted, Soraka's been the only healer left playing, but her awkward kit, lack of CC, and fragile defense makes her a weak pick.
Out of 10 on a "viability calculator", I'd give her a 5.5.