Ben was flat out horrible in the playoffs, and a major reason for the Cavs taking the series seven games, and for Miami dominating us. Look at the numbers Shaq put up against Ben, then check out the numbers he put up against Diop/Dampeer.
Honestly the team wasn't that great defensivly in the beginning of the season when they were on a tear they were like the 7th or 8th best defense and later in the season when the offense wore down, they improved somewhat defensively.
Now as the team stands right now, I wouldn't call them championship contenders, but its a long ways from the playoffs (hell FA signing doesn't even officially begin until tommorow). However I don't see any East team except for Miami as being able to take them in a series, even with the loss of Ben.