Surprisingly - Oasis is a very efficient for on and off - granted off takes a little longer than on (due to immigration control) but it is a very efficient port facility.
11:30 is definitely fine, but I would still try to get to the airpot as early asp possible. The lines get very long very quickly on weekend mornings.
I am the editor, but I also speculate, ask questions and play devil's advocate. I reserve the right to change my mind.