The Janna changes are EXTREMELY strong (perhaps even hotfix nerf worthy) but most people are building her wrong - Simple guide + video : r/leagueoflegends
Statistically winrates of support champions by game length (Patch 12.11) : r/summonerschool
Skarner vs Janna Build - LoLalytics Skarner Jungle vs Janna Support Build & Runes Guide
How to Find the Best Builds in League of Legends - Mobalytics
Kayle vs Janna Build - LoLalytics Kayle Top vs Janna Support Build & Runes Guide