The Spurs didn't tank to get Duncan. Their best player got hurt, didn't play most of the year, and their other good players fell off a cliff in production.
On the flip side, the team that did tank for Duncan, the Celtics, didn't get him.
Well I'm no professor in "Tanking" but there are different types of tanks..
There's the natural tank, there's the "man-made" tank, then there's stuff in between.
Natural Tank - is when your best player(s) goes down for the entirety of the season.
Man-Made Tank - situation I believe we're in right now when we make a conscious decision to trade most/all of our best players and be bad for 1-3 years.
Then there's stuff in between where your best player only goes down for half a season, but you shut him down for the entire season, trade out some players for picks during the season. I don't think it matters how you tank, it's the result you're looking for. Getting great talents that you could have for years to come.
Take that 2011/12 season for GSW. They already had Curry. The year before then went 36-46, but declined to 23-43, just bad enough to snatch the 7th pick from us which they selected Harrison Barnes. Curry, Klay, Barnes became their promising big 3. (Plus Draymond who they got in the 2nd round)
In 2011/12 you could argue they had the Natural Tank going with Curry being injured, but they also played Klay very sparingly down the stretch to get bad enough to dip down and snatched the pick to get Harrison Barnes.
Overall they were bad enough for a number of years to grab Curry, Klay, Draymond, Barnes - the CORE to their team and look where they are now.
2008/09: 29 - 53 - Drafted Steph Curry
2009/10: 26 - 56
2010/11: 36 - 46 - Drafted Klay Thompson
2011/12: 23 - 43 - Drafted Harrison Barnes & Draymond Green
2012/13: 47 - 35
2013/14: 51 - 31
2014/15: 67 - 15 - Won NBA Finals
And by the way - the majority of the CORE they had during the bad years are still with them today.
I think that is a GREAT blueprint and one that I believe Ainge is trying to replicate with the Jazz with the current rebuild.