Hi wyvern,
I was down there a few times last summer with work and really got the impression that exit immigration struggles with the number of agents vs. pax. I waited over 50 minutes when departing last July and suspect things haven't improved much in time for this year's either sadly.
My one tip is to make sure you are in the EU national queue if you have an EU/EEA passport. The queuing system is not very good as they often run out of space for the tensa barrier maze.