This build is for people who are bored of attempting to carry as soraka and want to play her the right way. Sure you have a lot less damage then a 'carry' soraka (early game) who just build ap. But late game you will most likely have dealt a ton more damage then the 'carry' late game. The reason why? You can stand in the team fight and take punishment, and still play your role as a support champion even if you get targeted (which you surely will.)

Pros:
Global heal (gives assists for mejais)
Lane sustainability is disgusting (as long as you don't spam star call to much)
Can initiate and be a tank ( Preferably not but hey you never know..)
Good poking with star call
Heals still heal pretty good
Farming is insane

Cons:
Squishy early game
Will and I mean WILL be targeted through out the game
Very stack depended (shouldn't be an issue after force of nature though)
Doesn't get EARLY farm in ranked games
Very mana dependent early game if you spam star call

Why play Soraka over Sona and other support champs? To put it simply she is the best.

Soraka VS Sona: Sona beats Soraka in heals early game there is no doubt about it. So shes obviously the better support right? wrong

(early game) Sona can spam her heals every 7 seconds the heal heals a simple 25 to two players and costs 65 mana a heal and only gets 25% ability power added to that and a small defensive aura. The problem here is that it costs 65 mana, in no time you will have no mana left and will have to go back seeing as how your heals do almost nothing.

Soraka not only has a defensive aura... Its her passive so she doesn't need to keep her heals going to get the same effect. Soraka's heal has a 20 second cool down, pretty harsh I know but they only cost 90 and heal for 70 + 45% ap which amounts to a little under 1/2 of what sona heals in that time. So why play soraka if sona heals more?

Their other skills is what is game changing for these two champs. Sona can only attack 2 people at a time and hits 250 + 75% ap when the skill is maxed and gives 20 AD bonus cause of the aura. Soraka's attack skill does 160 + 40% ap, this attack has no limit to the number of people or things it can hit. so soraka hits 250 on two minons that = 500 damage. Soraka hits 6 minions with 160 which = 960 damage.

Okay okay... Sure you can build Sona and soraka differently which will make sona hit more. But does sona have a silence that can stop multiple scary ult? Yes she does BUT! it is her ult, with a 100 second cool down im not sure your going to want to use it on nunu to save a team mate, instead of using it in a team fight and causing your team to ace. (and it doesen't stop all aoe ults since its a stun.) Soraka on the other hand has a silence with a cool down of 10. This can stop all those scary ults that stuns just dont. Like fiddle's and kat's.

ran out of time and i have to go will continue it later