For being so unmarketable he's certainly got a few Suns fans attention. Who says you can't market this guy outside of San Antonio?
Another thing worth noting is that while Orlando might not be a big market, Houston, the fourth largest city in America, is a big market. This city might be full of band wagon fans but when a team is winning they are certainly all on there.
As far as Tim Duncan goes, I really don't give a what the league needs from him. He plays for the Spurs. He does what the Spurs need him to do. Where this guy really loses me is the KG argument. I've never really found Garnett to be much of a dynamic personality. Barring his bizarre statements about going to war with the Lakers that got so much play I really can't think of anything that really demands a lot of attention. Then again, I also find Kobe and Shaq to be assholes. Maybe I'm the rare case of marketing success for the Duncan camp.