You're seeing it from the wrong angle though. There was no need to send him away in the first place because we should have given him the time to develop just like Marchisio did. Sending him away to Parma was the second best thing we could do. The best thing would have been given him a chance and actually played him regularly. Not forcing him into the starting eleven, but step by step getting him there.
I think you're nitpicking and concentrating on the small things that were bad. For an unexperienced player, Giovinco wasn't that frustrating that you could justify not playing him. You can't expect consistent magic all the time but for the big majority of the time he was actually doing something good out there. And his stats were mind blowing when thinking about the playing time he actually got.
Basically, he showed enough to actually earn his experience with Juventus instead of being sent to Parma. Usually, if a young player is as productive as Giovinco was with us, there is no way in hell teams would send him away, especially since we didn't really have the best squad at that time. Instead of sending him to Parma to get the experience we could have given him for free, but instead, we're spending around 7-8 million to get him back.
Also, I think Parma would have played a player with Giovinco's talent no matter what, even if they had an option to sign him or not. They're not that great of a team to not let him play. But thats a completely different discussion for now.