Janna's nerf won't do anything
What's the point in those nerfs? Yes, she's been the highest winrate support for several months, but realistically, what would you play if not Janna?
http://champion.gg/statistics/#?roleSort=Support&sortBy=general.playPercent&order=descend out of the top 10 picked supports there are 6 tanks and Morgana (a champ that Janna counters REALLY hard), the only champs that somewhat counter Janna out of those 9 are Soraka and Nami both being picked roughly 6% and 7% of the times in ranked.
So if i pick Janna i basically have more than 70% of the chance to play against a champ i counter.
Do you know wich are Janna's hardest counters? Poke-sustain supports.
Do you know how many times was Janna picked in S3? Nearly NEVER, because poke supports were relevant and strong, i was called a troll many times in S3 for picking Janna (now you get called a troll for picking Sona).
Now poke supports are irrelevant and nearly never picked, maybe it's time to buff them so i don't have to instalock Janna or Soraka every game in order to deal with tank supports, because that's really the only thing you can do nowadays.
Those nerfs are also really dumb (no offense): they will achieve nothing, Janna will still counter tanks as she's always done and her winrate will mostly remain the same.