I guess it depends where you fly into - our busiest queue was in Dulles (IAD) last year - but the queue management was excellent - they kept moving people into the shortest/quickest areas (even into queues that we were not entitled to be in according to the signposting LOL) so we probably spent between 1.0 to 1.5 hrs in the queue.But we had managed to fly direct/NS from our local airport so an indirect flight would not have been an advantage.
I think the DUB option would only really be worthwhile if it is significantly cheaper - as in Pauls case perhaps.