Is Janna really that good?

I actually feel like in the current state of supports that a lot of them aren't that much worse than the currently best one. They don't seem to unbalanced to me from my games of laning against all the different ones.

Now, if you look at my stats from season 5, you'll probably notice how good I was with Nami. I had a record of 163-132 with her and a 1.9-3.4-16.7 kda. And I pretty much got to platinum 3 just by using her every game. And she's not that bad now, at supposedly the 5th or 6th best support, depending on the source. And still, I found her to be relatively unimpactful and almost every game I felt mostly irrelevant this season and it just seemed like a coin flip to me as to whether or not my team would win. I only win half the time with her this season, even when I was in around gold 2 or 3 most of the time I was using her.

So what did I do? I was so worried that I just suck now. I just am not even better than some gold 3 players. I thought about why I didn't seem to have an impact on the games. My e barely did anything since it was like rank 2 or so for most of the midgame since I was underleveled. But worse than that was that being underleveled meant that I was kinda zoned out of doing much in so many situations since they strong enemies could just instakill me. I knew I wasn't really contributing much to a lot of my teams and it just felt so hard to win.

So what was the solution? It was simply to use that support that has so many ways to not die that I could actually help my poorly positioned teammates in far more situations, while still being safe myself. I started using Janna again, and OMG, she seems so much better to me it's unreal. Like check out my recent stats with her: http://i.imgur.com/FCbjAXv.jpg

My Janna can even win games that were thought by many to be nearly impossible. Look at this: http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2143832228/211539496?tab=overview 15 kills to 3 at 13 minutes and they had the dragon, and I made the Ashe so effective that we still won the game, even with a team that was full of feeders and people that weren't very good at teamfighting either. So, don't say that games just snowball and are decided really early on again if these kinds of comebacks are possible.

Now, is there some sort of explanation for how I could have done that much better with her, or is she really just that good?

Btw, support players, if you think you have no control over who wins the game a lot of the time, try playing Janna. I tell you, if you play her well you can totally own the game.