Normal games are THE PLACE to try out new champions. Go ahead and ban them in ranked play, no problem. But there is NO reason to ever ban a new champ in Normals. it is FREE PRACTICE with a new champion with NO REPERCUSSIONS.
If you pick a new champion: you get to try them out and get a feel for what they can do.
If someone on your team picks a new champion: you get to play around the champion and understand what to do in order to be successful with them in your team.
If an enemy picks a new champion: you figure out how to play against them and shut them down.
Please, don't ban new champions in normal games.