I'm afraid this is not just at Dublin - this is at every connecting airport. Including those of us flying from Dublin via a UK or US airport to elsewhere.
Quite simply, nobody officially trusts anyone else's security standards anymore - you must be screened to that country's "standard", even if they are identical to the one you just left. Daft, I know, but the way it is in this messed up, post 9/11 world.