I took the 7:50am flight last Friday.
Arrived at 6:10am. One person in the CE queue at the counters who finished just as I turned up. No queue at Fast Track security.
What did delay me was the high proportion of bags being selected for secondary screening. Unlike many other airports DUB requires eReaders to be taken out of any bag, same as laptops and tablets. They also seem very suspicious of cables, even if separately bagged.

As it's the first flight boarding can start at ~30 minutes before departure so don't hang around in the lounge if you want to be on early for overhead space