Dear Shalom,
Rabbi Blau is a master chef who can cook from scratch and probably doesn't need to follow a cook book when preparing a meal. There is no doubt that I would love to attend one of his shiurim if the opportunity presented itself.
I, on the other hand am a less accomplished cook who often will follow a recipe word for word especially when preparing a complicated dish, take something out of the freezer to serve, and when desperate I will even call for a pizza delivery.
I assume the requirements of ones class topics and schedule, the quantity and quality of shiurum level one needs to give, and how well and how quickly one learns all inform to some degree what level of original course preparation a teacher will be able to provide in a classroom.
Just because someone has Smicha doesn't mean they are prepared to answer a Shaylah on the spot in all four sections of Shulchan Aruch. This is the reason many Smicha certificates were given with Rav Moshe's phone number included. The same is true for a Rebbi or Morah.
Shalom,
Elisha
