Tutorial needs a bit more polishing. For instance, I'm told twice about the restart button and on level three I'm already aware that the torch guy can lit up places. It's okay to hold the players hand, when you first introduce them to your game. It's unnecessary to repeat your instructions to them, especially when I was just told about that on the level before.
Combat and movement needs a bit more work too. On level four or five, one of my characters apparently slipped and couldn't get back up on the platform so I had to restart the level.
Also, my question is why do I need a key to get to the door, when the mechanic is you can't finish the level without all three characters? In other words, I don't see the use of having a key, unless it unlocks some secret cellar or hidden chest.