Under Nolan, Miami's defense was Top 5 against the run. And, they were one of the few defenses in the league able to slow down Brady and his offense. The ONLY reason that Sparano's team didn't consistently beat out the Pats for the Division Title is because the Front Office refused to spend high draft picks on offensive skill position players. They had the defense, but a lack of talent on the offense kept them from scoring enough points. Far too often, Miami's defense would do great against "elite" teams, but their offense had to settle for FGs instead of TDs and they'd lose.
If Ross had only immediately replaced Ireland with someone who could recognize offensive talent. Give that team a big dose of talent at the skill positions while keeping the same defensive scheme, and they'd be at the top of the division every year... not the Pats! This is why I've HATED what Ross has done to the team. The Philbin hiring not only changed and ruined a good defense, but Philbin's offensive philosophy turned out to be even worse than what they ran under Sparano, and Philbin even had more talented skill position players on offense! Gase then continued what Philbin had started.
If Ross wants an answer as to why his team sucks, he just needs to look in the mirror. Instead of adding offensive talent to a good defense, he decided to completely change everything and ran the team right down the toilet.