A classic case of bad planning/ bad timing. Up to 2008 traffic at DUB was growing at 10% (?) per annum and the DAA was desperately trying to keep up by adding to capacity in a series of ad hoc measures. Then when they go for a proper new facility (T2 - which they should have done ten years ago) lo and behold, traffic starts to drop by more than 10% a year.
So they are left high and dry: a bit like many other sectors of the Irish economy. I wouldn't mind if they scrapped or mothballed Pier A and D. Save everyone a huge trudge in the case of pier D.