Sure we need also a new center or a Carter replacement as 6th & scorer...
But whats your solution as SF for the next years? Resigning Marion? Crowder? Granger? Marvin Williams? it HAS to be a very good defender. There is no other choice with Calderon, Ellis and Dirk as starter.
I just dont see a better one, so im fine with 15m for Deng.
Look at the FA SFs, its a short sad list (if you dont count James and Anthony)
http://www.hoopsworld.com/2014-nba-free-agents