I always watch videos as well, and have never had anyone tell me to do so. I do it because personally I don't want to hinder my party by not knowing what to do. I don't care if people don't watch videos, but I will always watch them.

But anyway, on to your idea.

My only thought on it is what makes you think anyone would actually use this "training"? I've seen many people say they don't want to watch videos because they would rather go in not knowing what will happen, and enjoy learning from wiping, than knowing what is to come. So this training wouldn't really do much for those types of players, and it seems like more of a hassle than anything really. I can't see people spending their time playing through a tutorial of a dungeon they can just queue up for and just ask people what they need to do, like it is now with those who don't watch videos.