Janna is still overpowered and needs nerfs, analysis inside.

Ok, top 1 support for 3 seasons, even with the tornado range nerf she remained OP. All her skills can deny a kill and that is massively strong:

Passive - Makes her team faster than your team, also lets her carry kite ez mode. Q - Instant knock up. If your team gets hit by a fully charged one it's game over. Too strong for a basic ability. W - It's basically a Nasus's slow combined with a passive that gives like 10 boots of mobility worth of MS. E - Not only it's a massive shield, but it also gives 2-3 B.F swords worth of AD. In lane your adc is guaranteed to win every trade and late game it's like they have 7 items. It also has 100% uptime with her max cdr she gets from OP items. R - AOE knockback combined with a massive heal, it's like 5 lee sins kicking everyone on your team at once combined with a health reset for her team, very OP.

Now let's see the items she builds

- Nerfed many times, but still the best item in the game. - Ward item, standard for all supports, but not OP. - Balanced item on most champions, but with janna's W passive it's just mega OP. She can go anywhere in 2 seconds and ward like crazy. - The aura is very strong. OP active that let her "Splitpush" without even being there. - Has the same Aura, but the active instead shields her team, combined with windspeaker mastery it's gold value is stupidly high. - Lol free QSS for your carry, combined with janna's innate peel it's impossible to kill someone she is peeling for. - Free damage for your carry, and janna can afford it because her overloaded kit allows her to do so.

Tl,dr: Janna is freelo, nothing can deny it. She just autowins bot lane... Even if the adc sucks she will never let them die. Her kit offers lots of shields/CC/heals/buffs etc, simply overloaded. Her items makes her deceptively tanky while giving lots of AP/utility (all her items except boots has OP actives).