Everybody knows the preseason games are meaningless as far as who wins and loses. You have to look at who plays and who they're playing against. Don't even try to compare our preseason games to the Colts and Pats. Everybody knows the Pats have nothing at QB behind Brady. I'm sure if Brady was in, they would have scored more than 3 points.
In Miami's case though, you can see some indication of what they have. It may be preseason, but their defense (worst in the league against the run last year) managed to keep the Chiefs starting offense from scoring when they had a 1st and goal from the 3 yd line. Are you going to try telling me that stuffing Larry Johnson (who you said is better than RW and RB) means nothing just because it was preseason? johnson had 13 carries for a measly 36 yds, Jones-Drew had 12 yds, and Fred Taylor had 7 yds.
It may be preseason, and the games may not matter, but I would say what the defense is doing against starting offenses deserves a little optimism.