I don't think averages matter tbh cuz every game is different. If you think you're missing shots you should be making, then practice aiming also if you don't quick scope, learn how to, I think that's the one of the most if not the most important thing to master with Ana.
I think improving your game sense as Ana helps more than actually improving your healing output. Like knowing when to anti, when to hold your sleep dart, where to position yourself etc etc