What's up with these claims about Miami having a superb defense - I disagree?

I think Miami's defense is border-line retarded. They have an aggressive defense - Yes, Fast - Yes, Intelligent - No. They often leave players wide open because all the defenders are in the paint. Just look at the number of times they left people open for 3 pointers, and even though Dallas missed most of those 3 pointers, it just goes to show if they continue to play that way, they are going to give up a lot of points