I played as Ana in a single comp game because the rest of the team was fairly set and we needed a sniper. We did really well, nobody really even died on my team. They couldn't cap the first point and it was on one of the easier maps to cap A. I saved two people just by healing them as they were being attacked or throwing the thing at them. I'm also pretty sure my ult at the last minute saved the game because it allowed whatever tank I ulted to clear the point.
Every other match I've been in, people are like, "thank god, a team without ana!!!" and I'm always really confused 'cuz Ana is REALLY good if you know how to actually be a support.