Using the Norris trophy is a bit misleading when talking about defensive play.
Doug Harvey won his primarily for his defensive play, when it was awarded for defensive excellence.
Orr was the first real rushing defenceman, aided by the NHL and WHA watering down the talent by going from 6 to 20 teams. He won his Norris trophies mainly for his offence, and offence has been the largest consideration ever since.
He was very good defensively, but not as good without the puck as he was with it.
I don't think most of your points are sustainable. You may be right that using the Norris trophy can be misleading when talking about "defensive play", but one reason Doug Harvey won Norrises was because of his passing and rushing (and PP) ability. It wasn't solely due to defence.
Your implication is that Orr's rushing ability was aided by the WHA watering down talent, but that is clearly false as he had won five Norrises in a row (which today would be the 2nd-most in history) and had three 115+ point seasons before the WHA existed. So that point has no merit whatsoever.
Then, as another posted pointed out, it doesn't necessarily stand to reason that Orr won the 1968 Norris trophy "mainly for his offence" when he was 11th on his team in scoring and 90th overall. There were nine NHL defencemen that year that outscored him, and yet he won the Norris with more than twice as many votes as any other player.
Then, as has been shown on this forum a few times before, polls of NHL coaches and GMs from the late 60s and early 70s show that Orr -- at that time, before the WHA -- was generally considered one of if not
the top defensive player in the game. So, if contemporary coaches and GMs didn't know the truth, then who did...?
And finally, during the four seasons prior to the WHA's existence, Orr was on the ice for 356 goals against Boston in 297 games played, or 1.20 goals against him per game. (If we eliminate PP goals against, he was on for only 230 goals against Boston in 297 games played, or 0.77 goals against him at ES or on the PP per game.)
Boston in total allowed 848 goals against in those same years. So, how much ice was Orr seeing? As he played a lot at ES, and also on the PP and SH, and as Boston sometimes had only four D-men with 65+ games played per season, you'd have to think he was on the ice for at least 30 minutes per game, or 50% of the time
at least. Thus, Orr (who also played the PK, don't forget) was on for 356 of 848 goals against, but as he missed 11 or so games, let's say it was probably 356 of 825 or something. At any rate, that number would mean he was on for no more than 43% of the goals against Boston during those four seasons -- probably less, if he was playing more than thirty minutes, as I suspect he was. Anyway, 43%, in itself, means his results were well above average for his team defensively in those seasons (and Boston was the fifth-best defensive team).
And again, if we just isolate his even strength results, he was on for, as I said, 230 goals against those four seasons, or 0.77 per game. So, let's compare those results with the other defencemen who received 2nd or 3rd place Norris finishes within these four years. Here are the results:
Bobby Orr - 0.77
Brad Park - 0.79
Carl Brewer - 0.88
J.C. Tremblay - 0.95
Tim Horton - 0.96
Bill White - 0.99
Ted Green - 1.08
Not one of these guys ever scored even 80 points in season (most half of that), and yet every one of them was on the ice for more ES goals against per game than Bobby Orr was. (Ted Green -- for three seasons -- is particularly notable because he was Orr's teammate and was a defense-only, shut-down kind of guy... Yet, his numbers are worse than Orr's defensively, despite less ice time!)
In conclusion: Since Orr's defensive results are better than all of these guys, just imagine how defensively dominant he'd have been if, like (most of) these guys, he
wasn't a rushing defenceman!