The upcoming changes to Janna's kit are an nerf in the early to mid game and a buff to the late game.
With a lot of base stat nerfs you probably want to look into investing Resolve rather than Cunning
Option 1: https://www.mobafire.com/league-of-legends/mastery-tree-planner#&tree1=0-5-0-0-1-0-0-0-0-0-0-0-0-0-0&tree2=5-0-0-1-0-0-0-0-0-0-0-0-0-0-0&tree3=0-5-0-1-0-0-5-0-0-1-0-5-0-0-1
Option 2: https://www.mobafire.com/league-of-legends/mastery-tree-planner#&tree1=0-5-0-0-1-0-0-0-0-0-0-0-0-0-0&tree2=5-0-0-1-0-0-5-0-1-0-0-5-0-0-1&tree3=0-5-0-0-1-0-0-0-0-0-0-0-0-0-0
Skill Order: http://prntscr.com/gl15d4
If you want further explanation about why these, you can ask them down below in here.
The Q change has its range increased and its travel time reduced. This means you can more reliably throw your Q in without having to worry about distance charge time.
Passive will always be up now regardless of the fact if you have W on cooldown + Movement contributes to our basic attack damage now.
E will have higher CD on shields, but will be same as before when at rank 5.
R has no changes.
Expect a change of pace with Janna, make plays early game rather than be a shield spammer. Be an engager.
(Super positive about the changes)