I dunno, while I agree the DUB-JKF-LAX would be good simply due to to the JFK-LAX A321T service, I would much prefer DUB-LHR-LAX. The J seat on the 77W far outweighs any of the seats you'll get on other routings, and you'd actually be flying long enough to enjoy it. Connecting on the east coast USA means splitting the journey pretty much in half and settling for an inferior product on at least one of the long legs. DUB-LHR is hardly worth talking about as it's such a short hop, Euro J would be fine.