To answer your question about loads to the west coast on previous flights,having operated many of them I can confirm that loads were generally very good in premier and economy on both destinations with cargo loads of about 10 tonnes each way.
This was rarely a cause for performance restrictions at Dublin with EIDUO having extra thrust if required.
This is a management call as they have the best figures and projections,
I would say it comes down to the future price of oil.