Brightwing, for several reasons a strong supporter who can interrupt e.g. E.T.C.'s Mosh Pit, Lily's Jug of Cups and support allies with increased movement speed and blocking.

Unfurling Spray on Lvl 1 increases the range of Soothing's Mist, your passive heal, which is first choice in this build to guarantee to heal all allies in your surrounding. When you cast Pixie Dust (E) on them, they will receive additional heal due to Manic Pixie on 4, which is truly important for talent on 16, because it will bonus heal AND reduce half damage taken on 2 allies for Shield Dust on Lvl 13.
Mistified on Lvl 7 grants much more frequent passive heals. It's no big deal to achieve 80k heal points and more in a 20 minute game with this build.

First choice for Ultimate is Blink Heal (R) to quick heal assassins in the backline, but you should avoid to heal warriors to not get focused. The amount of this healing is low to medium in comparison to Rehgar's 'Ancestral Healing', but the combo of passive and active heal can be defining. For the talent on Lvl 20 I suggest Revitalizing Mist and Storm Shield.

Have fun with Brightwing, a mighty healer.