No it doesn't it sucks the enemy closer to the ball, no matter where ori is.
Diana has High HP + Shield, she WANTS all 5 enemies sucked on top of her, she tanks while her teams blows them up.
1) Ori generally isn't with the ball- if she is, she's an idiot.
2) Diana is the one supposed to be 'blowing people up'. If she's getting gangbanged by everyone on the other team, then you just lost your AP Carry, one of the key elements of your whole team.
Diana is strong against most champs in the entire game.
I dont want to be stuck playing 5 out of 105 champions just to stand equal to such an OP champion.
Well, different champions counter other ones- they're BUILT to do that. If you're facing an assassin like Diana, then you'd be an idiot to go with a squishy like Cass. If you tried actually playing as Swain, Morde, Ryze, or Cho, then you'd notice that she's actually weak against tankier champs.
Furthermore, Diana's kit DOES have weaknesses. For one, she's a melee champion, so someone with poke (for instance Swain, Morde, Ryze or Cho) can eat her alive. As well as that, she relies on getting into melee in teamfights, which as I said earlier, is extremely undesirable in an AP Carry. Her only ranged attack is an easily-dodgeable, relatively short-ranged skillshot that has low enough damage already and is getting nerfed to 200 max (!!!) next patch.