-Put some emphasis on Vlad MID because if he falls slightly behind a tank early while in the top lane, he is useless for the rest of the game.
-Galio is super duper strong vs AP, however, even in favorable matchups it is hard to carry as Galio due to his weak pushing power (Turret destroying).
-Maokai is team reliant. I agree that he is strong but he is support strong and not carry strong.
-Yorick is a strong lane bully with a little bit of carry potential. I think Yorick is the most significant champion you mentioned in this post.
I do not believe that any of these champions are OP at all. I do believe that they are all sleepers though. I think Vlad is the weakest on this list due to the problems he can run into if he is in a unfavorable matchup. The rest of the champions on the list can still provide strengths when they are in unfavorable matchups.