Janna isn't OP.
I saw some Low-elo's Janna QQ thread on the frontpage and just stated loling.
It's time to admit when you guys are just bad.
Janna is good in ranked cause people don't care about team comps and just pick whatever they feel like. Janna naturally screws some champions harder than others with their abilities, but not all. Learn to pick against it or champions that can deal with her. Or, the best option, just ban them if they give you so much trouble and stop complaining.
There is a reason Janna isn't picked or banned much at all at the professional level. (It's because they suck.)