Schematically, the Bulls' defense isn't impenetrable. Every scheme has a counter-scheme and the Bulls' is no different, other than the counter requires more intricacy.
The Pacers and Hawks each pulled off a win by heavily shifting the weight of their offenses and attacking off the ball on the weak side. The problem is that this is easier said than done because the Bulls recover from shifting the weight of their defense so fast that Indy and Atlanta needed two or three very quick, pinpoint passes on large quantities of possessions.
With players so elite as LeBron James and Dwyane Wade -- notably Wade's timely cuts and James' elite passing skills -- the Heat have the option to terrorize the Bulls' defense, though they'll expend a lot of energy doing this. Chris Bosh had a very strong Game 1 doing just this, but with shorter cuts through slots in the Bulls' D, as he's positioned closer to the basket.
James and Wade may be the most dangerous rim attacking combo in the NBA and this forces defense to put these two strong FT shooters at the line. The only successes against them in the W-L column was preventing them accumulating those points, though:
The Bulls held James and Wade to 30.0 PPG combined at the rim/line in the two games they met in the regular season:
The Bulls held the two to only 18 combined points at the rim and line in Game 1 of the Eastern Conference Finals. James was only 1-for-4, but Wade was a strong 4-for-6. The difference-maker was that both were each held to only 4-for-4 at the line and were blocked a total of three times, showing a pretty low quantity of them even being able to attack (Hoopdata).
The Bulls' NBA-best defense is a scheme Tom Thibodeau install in Boston, which they continued. Regardless of the personnel, the spacing on paper is similar and look how James and Wade tore apart Boston's spacing, neutralizing the Celtics' skilled height advantages (John Schuhmann, NBA.com):
The Heat were successful running James and Wade on opposite sides with the ball in the PG's hand with Bosh at the high post and the center around the low-mid post, Brett Koremenos noted (HoopSpeak). It's an option where neither are primary ball handers and one of the two get the ball later in the shot clock on a second pass from the high post, inducing a Bulls "blitz", and the other with Bosh finding slots. If you don't blitz, James or Wade attack at will. The key for the Bulls is helping the helpers and recovering quickly from the blitzes. So hard to do because the less you commit the help, the harder James or Wade can attack and the less likely it can be stopped without sending them to the FT line.
It will be imperative to effectively defending the Heat that the Bulls don't brainfart on what's so heavily contributed to their successes against Miami in the regular season and playoffs this year, Schuhmann noted before the Bulls-Heat series began:
The Heat are a great defensive team, so they can still win games when their stars aren't getting to the basket. But if you can keep them under 30 points near the rim or at the line, you're clearly doing a pretty good job defensively, and you're giving yourself a better chance to win.
One reason the Celtics had a tough time keeping James and Wade away from the basket is that there were usually two of them on the floor. And when one of them had the ball, the other wasn't standing around and waiting.
When James and Wade decided to play together last summer, they each had to find ways to be effective when the ball wasn't in their hands, or else the Miami offense would risk getting stagnant. And one way they've been able to make an impact is by cutting to the rim from the weak side, which they both did effectively in the conference semifinals, as you can see in the adjacent video.
It's a part of their games that has evolved as the season has gone on. In four regular season games against the Celtics, just four of James' and Wade's 32 combined field goals near the rim were assisted. But in the conference semifinals, 20 of their 47 field goals near the rim were assisted. They were getting a lot of those buckets via ball and player movement, rather than strictly on individual drives to the basket.
Two of those "better defenses" are the Celtics and Bulls, who both like to load up on the strong side of the floor. As you see in the video, when the Celtics help defenders focused too much on the ball, James or Wade made them pay with off-ball dashes to the rim. And if the Bulls want to do a better job of keeping James and Wade away from the basket, they've got to do a better job than the Celtics of denying those weak-side cuts.
Using Hoopdata and only including players with 40+ GP and 25+ MPG with 3.5 attempts per game at the rim, James' ranked 9th in FG% at the rim and Wade tied at 28th -- with a still high percentage -- in the 2010-11 regular season. What sticks out like a sore thumb are the low percentages at which their FGs are assisted. Combined with the high frequency of their trips to the line and their shooting percentages, this is a numerical representation of some dangerous high-volume dribble penetration (all figures per game):
(For contrast, Derrick Rose surpasses every eye test as one of the most dominating basket attackers in the NBA. His FG% at the rim was .600 in 6.3 FGAs per game with an .858 FT% in the regular season.)
The low percentage of Dwight Howard and Andrew Bynum's rim buckets are easily explained by putting back second chance points, as are usually the cases for unassisted buckets at the rim by bigs. It's point guards like Rose, Deron Williams, Steve Nash, Chris Paul, Russell Westbrook, and Tony Parker who fall below James' rate of assisted v. unassisted rim buckets -- and that's inflated by the extreme frequency at which James and Wade are fouled while penetrating into a shot.
The Bulls could take an ass-whoopin' on any given night to the Heat because of James and Wade's aggressiveness, but the burning question is now: can the Heat expend the energy necessary to execute so aggressively to win four of the next six against a Bulls team much bigger and faster than the Celtics?
I struggle to understand how that answer is yes.
Though I'm eternally baffled as to why James doesn't exploit his .700+ FG% at the rim and .750+ FT% -- with his enormous 6-foot-9 260-to-275 lb. frame and quickness -- to overkill his efforts to attack the basket, he doesn't exploit that as much as he can. He's unstoppable when he attacks the weaker (everyone); and the greater the effort to stop him, the wider the off-ball lane Wade has to rack up and-1s at will.