In the meta not very viable atm but same for mercy, u cant Pick her in any comp.
In lowelo u can play ana, u can Climb with every hero, but in mid master+ they will counter ur ana with a Monkey.
The Monkey doesnt even need to kill you, he just need to shield ur mates and then u cant heal them, thats anas con. (But Jeff is telling every week that he'll Work on it, he just wanna wait how Brigitte will Change the meta cause anas kit isnt weak- just offmeta)