The A350 can't use Dublin fully loaded for the same reason, will only be able to go to ORD, YYZ, JFK, BOS and possibly MCO with a full passenger load. I wonder what EI has planned for them, since they have got 9 on order.......
The issues surrounding DUB having one of (if not the) shortest main runway of any primary airport serving a European capital have been discusses around this parish a number of times. When EI were placing their A350 order the new 28R/10L was still expected to be built this decade and it was planned to be 3110m long, as opposed to the 2637m of the current runway.
JAS