Didn't think cc were allowed to be of aircraft on international flights, could be different in DRW though. 170-something pax... what's the full load for the 320, I thought it was around the 150-165 mark? Aren't they using the A330 for JQI flights?
As I said, QF don't have cc at the gate on international flights... I am one so I would know. Not even on the 737, it is all done by ground crew. I agree with experience one can recognise MOST pax showing signs of intoxication... but some don't show it. Once knew a guy who could have 8 beers in a short time and still speak normally, without any sign of slurred speech or unfocused eyes. Point is there will be ALWAYS someone who gets pax, even if the cc are on the ball- as there are plenty of other things to be looking at during boarding as well. Often, you don't realise until after they walk off and the alcohol smell wafts up. In which case it's seat number noted and quiet chat prior to t/o.