The Heat's defense thrives on trapping the ball handler; sending them out way beyond the 3 point line and jumping the immediate passing lanes, leaving the 2nd pass to a shooter open. They gamble on being able to intercept the first pass and being able to recover should there be a 2nd pass. They have been quite successful this series as well as all season.
What I've noticed is that whole defensive concept is predicated on the double team trap of the ball handler. Their trapping is aided even more so by the pick and roll. When the ballhandler calls for the pick, the screener brings his defender with him. Instead of switching they immediately go for the ballhandler.
So if I were the Spurs I would stop running the pick and roll with the ballhandler. I would primarily run picks and off-ball screens, with the other 4 players to get open shooters, cutters and passing lanes.
Also I have faith that Parker and occasionally Neal as the ballhandler can take his man off the dribble and draw a double team. But in this case the double would come from inside the 3 point line and would allow for much easier passes to be made.
And in the even they bring the double to the primary guy early. The 2nd defenders offensive man should have more ability to exploit his defender leaving him and at the very least give the ballhandler an easier passing lane.
tl;dr Heat's defense is perfect pick n roll counter. Stop running pick n roll with point guard. Off ball-screens and cutters and iso penetration to achieve same results as pick n roll did previously
tl;dr tl;dr Heat double team good, pick n roll bad