LeBron driving into three and four defenders just isn't working. Gibson, Marshall & Pavlovic are going to have to drain their threes for the Cavs to win.
Also, I bet Mike Brown didn't see this, but there was a play where James got the ball in the high post and passed to a cutting Marshall for a (clumsy) basket. That's one way to combat what Detroit's doing without relying on outside jump shots. If they're going to sell out to guard LeBron, then don't do it by clogging the lane - get him the ball in the high post and send people to the rim. LeBron will find them, and they'll get higher percentage shots.
Also, Tayshaun Prince is my favorite non-Cavs player, but to say he has been a great defender in this series is a mis-statement. When James has struggled, it has been because they have been bringing three and four defenders at him. Prince cannot guard games one-on-one.