That was my point. In 1999 and 2000, the Kings didn't have a great defense, much like Phoenix last year. They added a few pieces and became the #2 defense in the league by 2002-03 (#1 in FG% against). It took a few years, but each time they made little improvements and ended up not only as title contenders but as favorites. So, if you add a little D to a team "without D", it does make a difference. It appears that Phoenix is trying to do the same thing. (I put "without D" in quotes because Phoenix actually had decent defense last year - ranked right in the middle of the league).
And, as I said, I sure hope adding a little D to a team "without D" does make a difference, otherwise the Kings need to start re-building from scratch. I don't share your pessimism on that subject, though.