Her head hitbox makes her insanely vulnerable to Widow, Hanzo, and McCree. She feels powerful but at the same time she seems weak. They tried taking the best aspects of several heroes into one, and it just didn't pay off.
The mini-graviton has situations where it's amazing, but most of the time it's to stop someone stalling for a second or two. She's exceptionally good at holding one angle while Reinhardt's shield is down, but she's so bulky and vulnerable that I'd never run her without a Reinhardt. Her ultimate ability, like her playstyle, is all about holding a single angle. She's not terribly good on KotH against a decently coordinated team, due to the varying angles they can attack from. Her shift ability is pretty mediocre. I love watching newbie Orisas use it into a whole hog. The best use for it honestly is just kiting people, but that's hard when she's built around holding angles and is not terribly mobile.
Ultimately, she's a decent death ball hero. She's arguably more of a turtle hero, since she and her shield aren't mobile, but that's a death ball nonetheless. Her biggest counter, other than snipers, is dive composition. She can't escape a dive, she can only try to out-DPS or tank it, which is hard against a coordinated team.
