Janna doesn't look like much, yet was very strong for a very, very large part of Season 12 . What's more, the rare times she wasn't top tier, she was just strong . Yet it has escaped the nerves of Riot Games for months, as well as the vindictiveness of players who do not complain specifically about it. But, ultimately what makes it so OP?
A farted kit?
Even though her spell kit looks relatively simple, Janna has a great argument, while being able to adapt to most situations. Already, his ultimate is never completely useless. It's one of the best peeling tools in the game , and it provides an acceptable amount of healing, although well below that of champions who specialize in this area. The Air Avatar additionally has one of the best passives in the game, especially at high Elo . Any source of passive mobility is good to take, and it helps not only to evade opponents in a teamfight, but also in the lane phase where it becomes easier for the ADC and Janna to dodge enemy skillshots.
In terms of the CCs it brings, it's still pixel perfect . His slow (Z) is ok tier, strong without being abused. On the other hand the tornado (A) is incredible. Firstly because it's a knock-up, so the best CC in the game . It is also relatively long, can hit several opponents and makes fights in the corridors very difficult for the opponents to manage . Janna may not be very good at initiating actions (the R flash in the middle of the enemy team is much more often int than a play at 200 IQ), it is still very difficult to engage against her team. She's a champion who can catch up with her allies' mistakes with her peel, a very important thing in soloQ especially when your mates are a little too prone to tunnel vision.
Favored by the meta?
If we left out Janna's main spell in the analysis of her kit, it's because it deserves its own paragraph. His shield (E) not only absorbs a more than respectable amount of damage, while providing a lot of AD. This amount is equal to 30 AD at max rank , not counting the bonus provided by Janna's AP (+10% of her AP), which is more than a pickaxe . Finally, the value of the shield is increased by 15% if Janna has applied a knock up and/or a slow in the 4 seconds preceding its activation . This makes a duolane with Janna much less passive than with other enchanters, allowing her ADC to easily punish enemy aggression. It is difficult to try to trade against a lane with Janna, because if one or more skills of the ADC or the enemy support are dodged, Janna can put down her slow then shield her ADC, which can put a full rotation of spells easily.
And this is where the importance of the meta also comes into play. Even if some AP champions distinguished themselves in season 12, or were even broken, there were always very strong AD champions. By imagining that Janna's lane is going badly, she can not only be a thorn in the side of the opponents thanks to her kit, but can also decide to help the AD character of the team who is not too bad . Although Janna will rarely be the main carry of a team, she will remain very strong in almost all situations, which explains her winrate.
TFT welcomed a new set a few weeks ago and players were able to discover new synergies and champions. But there is one, hated on League of Legends, which exasperates the community a little more with each game...