There has been plenty of discussion about inconsistent AC systems over at vwvortex. If you have a VCDS you can check to see if you have "Hot Country" enabled. It seems like there are some cars sold that had it enabled and others that didnt. Reading through the thread below, people have reported getting cold air much faster after making the VCDS tweak.
http://forums.vwvortex.com/showthread.php?7974521-2015-GTI-VCDS-AC-quot-Hot-Country-quot
Instructions from the link above:
1) Open VCDS
2) Go To Select Modules
3) Under the "Installed Modules" window - select number 08 - Auto HVAC
4) After the control loads - select Coding - 07
5) Click the button for "Long Coding Helper"
6) Press Tab or arrow down key until you see "Byte 12" selected
7)Under the drop-down for "Bit 4-7" select "10 Temperature Adjustment: Cold (Hot Countires)"
8) In the top-left corner of the window - select the "Exit" menu item
9) Press the "Do It" button to save the new setting
10) If all goes well - you should see a popup "Coding Accepted"
I haven't done this myself or checked what my setting is since I am happy with how my AC performs. Might check just to see what my settings are just for kicks.