Here's what I like about brightwing.

1 (W) Polymorph! It's an instant cast CC with a decent range. You want to turn the tide of battle? Turn that spinning Valla who just used strafe into a peacefull squirrel. Nazeebo thinks he's cool using Ravenous Spirit in the back? Turn him into a happy little pig. Poof, no more ghostman killing your dudes. Only Ulti you can't CC someone out of right now is Diablos fire breath

But isn't it dangerous to go towards the backline of an enemy team? Not if you're brightwing

2 (R) Blink Heal! If you can keep pace and awareness up you will be able to Blink Heal from behind enemy lines to the back of your own line. While Healing. You don't even have to worry about people focusing you, cause if they do they are wasting their time. You can Blink Heal to minions as well as teammates. This provides a lot of opportunities to run people in circles.

But all that blinking must use up a lot of mana right? And Brightwing doesn't get a cool mana regen, right?

WRONG.

3 (Z) Phase Shift! You have permanent access to the fountain. Whenever you find a chance just hearthstone back to fountain, and global teleport back into the fight. Full mana and health. You will miss 5 or 6 seconds of combat, which could be vital, so use it wisely. A powerful tool none-the-less. Even if you aren't using this as a means for just getting mana back, having a global presence with good map awareness is OP on it's own. You can turn an early fight in a different lane into your teams favor at an instant.

This isn't even mentioning his AoE passive heal, (Trait) Soothing Mist, which when combined with the level 7 talent Regenerative Rains, will top the healing charts.

I went up 600 MMR (2400 - 3000) on hotslogs by only playing Brightwing during the holiday event. 70-75% win rate over the course of 50+ games. I've been meaning to put together some Brightwing montages highlighting some of the ridiculousness that Brightwing can pull off.