The Janna changes are EXTREMELY strong (perhaps even hotfix nerf worthy) but most people are building her wrong - Simple guide + video : r/leagueoflegends
Based on lolalytics Samira already has a 49% winrate on botlane : r/SamiraMains
Janna holds the highest Top Lane WR in patch 10.4 : r/leagueoflegends
Some Janna Stats from lolalytics and a few rune tips! : r/Janna