In regards to him playing the "deadwood", I think McClaren has the right (and is right) to give everyone a chance. He'll want to see everyone for himself before deciding on what his best team is. Any manager would do the same thing.
I agree that some of his team selections thus far have been strange but we don't know where these players are in terms of their fitness, how they look in training etc. as well as injuries to certain players like Coloccini. If he persists with the likes of Obertan being in the squad once the season is under way and players are at full fitness then I'll start to question his team selections.