He wasn't ineffective vs Miami. THere is a reason the leads evaporated to nothing while he was off the court, and they extended leads while he was on the court.
The only reason why people said he was "ineffective" was because the idea that he must be a scorer. It's just a horrible way to look at his game. On the other hand, people look at Tyson Chandler, and completely understand he offers nothing offensively so they don't expect it. They only judge him on his ability to anchor a defense and rebound, something Roy Hibbert did on a similar level.
By the way, Roy Hibbert being able to effectively hinder the offense of a team that has Both LeBron James and Dwyane Wade is incredible. His best series was against Miami. Not Orlando.
He's just fell flat on his face this season and I'm not sure why.