Orianna's gameplay revolves around the ball. With her q and max range being within most gapclosers and stuns, I think the risk to reward ratio is too high to use it effectively. Her w is a great utility and offensive spell except that its tiny, a huge part of her damage, and on a high cooldown. These weaknesses are all highlighted against a team with good mobility, you would have to have unnaturally good reflexes and ping to get a prediction on where the enemy will be.
Her ultimate is not exactly stellar either. Her e is very constricted and I have mostly used it to set up for an ult. However if a teammate is unaware of the ball, it snaps back.