Just revert the buff to Orianna's ultimate
As in: increase the cooldown. She didn't need that buff to begin with. You just made the change to force her into pro play. Orianna's fine in solo q though (imo). People just love complaining about champs they see in pro play because they somehow think it validates their opinion. Team fight centered champs will always be stronger in pro play and could be relatively balanced in solo q.
10 seconds more on her ult is reasonable though.