She's flooding quickplay, and no one knows how to deal with her super yet.
Right now, on console non-KotHmaps, a nano'd Reinhart or Genji basically means congrats on your object capture or payload checkpoint.
Them healing is totally hit or miss (heh)...
I played a game with two Ana's on my team and didn't get a single heal the whole game as a Roadhog and Pharah.
But I know she has potential. My wife and I played a game in a group of 6 last night with her as Mercy and me as Ana. She ended the match with like 4,700 healed, and I silvered at 3,900 healed. It was a pretty quick attack on King's Row.