When should I play Soraka Mid?

• If your ally support is not a healer!
• If your jungle and or top laner is a heavy dive/bruiser champion like Sett or Udyr!
• If you WANT TO!!!


When should I NOT play Soraka Mid?

• If your ally support is a healer!
• If your jungler does no damage(supports the laner) and or does not dive such as Skarner or Karthus!

Pros / Cons

Pros

+ Crazy high healing power coming from the MID laner.
+ Map wide pressure with Wish
+ Safe in lane, hard to abuse if she is positioned carefully
+ Healing from W is unexpected when your Jungle ganks, making winning ganks easy
+ Strong poke in lane, Equinox is great for shutting down any channeled ultimates like Katarina or Vel'Koz
+ Self sustain with Starcall is much stronger
+ Raka's healing scales off AP, so with majai's you'll be healing like crazy
+ Most items are relativly cheap

Cons

- Very susceptible to ganks in the very early game, play safe
- Relies on ganks from your own Jungle, if they don't gank you, you're in for a rough game
- Very squishy and often a priority target in teamfights, try your best to keep those mejai's stacks!
- Reliant on her team to protect her, can be troublesome if team is unwilling or unable to do so (which is often the case as mid lane. so be prepared to fight for your damn life)

How to play this build.

Early Game:
It's relativly simple. Play your early lane safe since you are an easy gank target, but get as much poke in as you can. They usually don't expect the damage since you are a Soraka so sometimes you can even get a free kill.
But for the most part just focus on farming. And assisting your jungler ganking your lane.
You're basically a support but instead of for the ADC you're supporting your JG ganking your lane, early game at least.

Mid Game:
At this point in the game, where laning phase has ended you won't be getting much more CS since your team will be holding/pushing lanes. So, buy Relic Shield and group with your top laner or whover is alone solo pushing a lane. Now in team fights and such you wanna focus on healing, not damage. Even though you're the mid laner. Get in damage where you can, of course. But healing is the main priority.

Late Game:
Just play with your team! Stick with them and support! It's really simple.
At this point in the game you really are just a heal bot. Just don't get killed and heal your team.

A few quick notes on runes:

Scorch over Gathering Storm may work for you. Taking Scorch will give you tons of poke damage early game with Aery procc. It's really just user preference.

You might be asking "Why would you take Font of Life on Soraka? She only has her E stun."

That's exactly why. As a mid laner turned support late game you need the extra utility you get out of FoL from landing her E root to get just that much extra value supporting your team.
Especially when you are going into a team that doesn't have any major abilities that need silencing.