Is Ana useless ?

Ana is kine like the Mcree of support. If you have the aim necessary, then she'll shine. Add in some experience & good teamwork, and you can use that awesome sleep dart so so well.
I really like playing as her, and although I won't usually get POTG, in my head when you sleep an ulting pharah near a cliff, you feel good inside :p

No, any champion it's not useless. It depends on your skill with Ana... I can be the best support and also the worst support. It all depends in the comp that you're playing against

no is good hero da good real good i thth (so se><y)

Ana is useless for me and I personally prefer Mercy more than Ana

Not that easy to determine such a hero, since that Ana in low elo can easly carry games solo handed. But on the other hand it can break a team comp from simply a lack of defensive ult. In that case Moira or Zen can easly replace Ana.

I really like playing with Ana's. She is hard to play but in higher ELO people usually know how to play her very well and she can be very effective.

She has the highest heal per second output, next to Moira. Also, she is a very good counter pick to help offensively. For example, if the enemy has a pharah but your team has limited/no hitscan, she can by the primary killer of her