OMG 737's should not go across the pond, it is difficult enough flight to say the Canaries or Egypt from the UK on these birds in that cramped cabin.
Purely as the crow flies:
Dublin to St Johns = 1781 NM
Dublin to Las Palmas = 1581 NM
Dublin to Luxor = 2406 NM
So, in that context it's quite acceptable. Yes, you then have the same distance again to the Dominican Republic, but you get watered and fed...
Think about Southwest and its Providence-Las Vegas flight: 2053 NM as the crow flies aboard a 73W. In fact, Southwest has a fair number of routes above 1,500 NM.