For one thing, I appreciate that someone has taken the effort to really put together a very good team predicated on defense. You've done a great job with that team. One thing I'm amazed is how little your team is fouling; are you running slow down? I have a team right now with over 300 fewer fouls IRL that's committing over 17 fouls per game right now.
As to your numbers - looks like you did some pretty good research. A couple things: first, I believe you're in an open league. Good teams in open leagues often have their numbers skewed by horrible teams, which you pointed out in your post - I'd be interested to know how your team's numbers look when you take out the awful team in your division.
Second, the issue isn't really how much teams are scoring per possession, or that offense is overpowered. It's that defensive ratings don't seem to provide enough of a difference to make them worth the salary in most cases. There doesn't seem to be much difference between the effect of a 90 overall defender and a 70 or 60 overall defender, and that's what people mean when they talk about defense being broken - that there's not enough of a discernible difference between elite and good defenders, good and average defenders, etc.
For example, let's look at a more balanced league than an open league - the most recent iteration of the ODL (original draft league), NBA 33483. My team had the best field goal percentage defense in the league - 48.0%, with my team averaging over 9 steals and 9 blocks a game. I had 7 players who played more than 7 minutes a game - their defensive ratings were 96, 90, 82, 80, 80, 50, and 39. The two guys at 50 and 39 played mostly at the same position, so I usually had 3-4 players with 80+ defense on the floor at the same time; plus, those 5 players with 80+ def were a PG/SG, SG/SF, PF/C, PF/C, PF/C so I had most of the court covered with excellent defenders. You would expect that to be a very good defensive team - and yet 48.0 pct from the field is all, even with a healthy number of blocks?
Another team in my division had a 7-man rotation with defensive ratings of 94, 79, 65, 63, 59, 56, 50 - not nearly the amount of high-level defenders. Yet that team - while blocking 2.4 fewer shots per game - allowed 49.4 pct shooting. Considering our opponents both took under 100 shots per game, that 2.5 blocks per game more than makes up the difference in field goal percentage, Outside of the blocks our teams essentially defended the same - do you think that sounds right?
Note: I realize this is an over-simplification. But anyone with a lot of teams in the sim over the last year or so can tell you that, for the most part, defense is not worth what you pay for it.