I had the same dct lag issues when I first got my car. The dct update from the dealership helped but didn't completely solve the problem. I had OE tuning flash my dct when they did my ecu and that did the trick. I don't have any lag in D mode and the shifts are smoother & quicker in S. the dct flash also lowered my launch control to 4000rpm which makes a huge difference! I don't sit there just spinning my tires anymore lol.
You guys should consider a dct flash from one of the tuning companies. I think that'll be the solution to your problems