Yeah, but Duncan knows better than to be that aggressive in that atmosphere. He's playing against people who would rather fade and hit a 20 footer than go to the hole. Give 'em some space in tight. That said, it definitely hurts.
Dallas was a statistical defensive team, but that can be accomplished by impacting pace of play. They have a couple of guys who play good D, but that doesn't help when you have Terry and Dirk to cover for. Good D is the team who can make the stops when needed, not those who change pace of play to statistically decrease total points of opposition. Good FG% defenses are sometimes great, but they are more often teams with a good backstop who prevents crip shots, which generally help the O's shooting percentage.