What team comps are you playing against with Ana that sleeps are hard to land. Sure, sleeping a Genji is hard, but not a tank. And it’s really hard to miss shots with Ana on tanks. Try playing her in more of those comps?
As it stands, funnily enough I’d rather play Ana than say Mercy against any dive tank. Her escape really isn’t enough against a persistent Winston. Same for Moira. But Ana can easily land a sleep on him, and either get her team to finish him, or simply walk away.