They should do a mini rework on her. This is what I propose:
Passive : Same as currently, but a bit longer range.
Soraka gains 70% bonus movement speed when moving towards allied champions below 40% of their maximum health. EFFECT RADIUS: 3000
Q : Same as pre-rework Q but no MR shred. In exchange, increase the base damage a bit.
RANGE: 530 COST: 30 / 35 / 40 / 45 / 50 MANA COOLDOWN: 2.5
DAMAGE: 60 / 85 / 110 / 135 / 160(+ 40% AP)
W : Current W, but with higher mana costs since it won't require HP.
TARGET RANGE: 550 COST: 90 / 100 / 110 / 120 / 130 MANA COOLDOWN: 8 / 6.5 / 5 / 3.5 / 2
HEAL: 80 / 110 / 140 / 170 / 200 (+ 60% AP)
E : Current E, maybe make the root duration a tiny bit longer and lower cooldown since it's not point and click.
TARGET RANGE: 925 COST: 70 MANA COOLDOWN: 20 / 18 / 16 / 14 / 12
ROOT DURATION: 1.25 / 1.5 / 1.75 / 2 / 2.25 DAMAGE: 70 / 110 / 150 / 190 / 230 (+ 60% AP)
R : Current R. No changes except maybe some number tweaking.
EFFECT RADIUS: Global COST: 120 MANA COOLDOWN: 160 / 145 / 130
**HEAL **: 150 / 250 / 350 (+ 60% AP)
I think this would make her viable as a mid laner again if you want an off meta pick.
Numbers for all of these can obviously be tweaked