Best Support?

Taric. Despite the nerf to Resolve, Taric has possibly the most game-changing ability in Cosmic Radiance. The ability to get invulnerability onto multiple teammates for a full 2.5 seconds is often enough to win a team fight or the game on its own. Any level of coordination when engaging with Taric and someone like Zac, Jarvan or Camille can be absolutely fatal for the enemy team.