Ana is a very strong off healer, but she requires decent communication to pull off to her full potential. With smart play, she can essentially make any 6v6 a 6v5 for a couple seconds, which is stupid powerful for an ability with only ~15 second cd, and she will hard counter other healers with good use of her grenade.

Even if she didn't have her ult, I would say she's still incredibly powerful with some coordination.