We just got off the Fantasy a few days ago.
Our drill was on deck 4 and they had people shoulder to shoulder (we were told that if you were not rubbing shoulders with the next family you had too much space and they had to squeeze in 10 more families) each family lined up in a single file from the wall toward the railing (short person first and tallest behind) and it got very hard to breathe quickly and many people had to get out of line to get some air.
Some people were late and it took a good 30 mins (thankfully we had water with us) but I would recommend a portable fan as well. There was an occasional breeze but with hundreds of people standing so close there was little airflow.
It was a sold out ship. We were so exhausted from travel (6 hr flight delay (2.5 hrs stuck on the runway) meant only slept 1.5 hr the night before) and the drill that we skipped the sail away party and just relaxed on the loungers afterwards. There was a nice breeze once the ship started moving.
When we cruised before (a decade ago) our drill was in the theatre and it was nice and comfortable with the AC. I would seriously reconsider what room we book in the future.