I don't think the OP is suggesting that the same crew will fly ADD-DUB-LAX-ADD, merely that the aircraft doesn't have to stop in DUB both ways for crewing reasons. (I recognise that it is stopping both ways, so the point is academic.)
Monday:
Crew 1: ADD-DUB
Crew 2: DUB-LAX
Crew 3: LAX-ADD
Wednesday:
Crew 4: ADD-DUB
Crew 1: DUB-LAX
Crew 2: LAX-ADD
Friday:
Crew 2 or 3 (or other): ADD-DUB
Crew 4: DUB-LAX
Crew 1: LAX-ADD
and so on.
Apparently ET have fifth freedom rights DUB-LAX and v.v. so eastbound is would have to be LAX-
DUB-ADD, not LAX-ADD, otherwise there would be no point.
Maybe the B787 can do it in one go, maybe there could be 2 pairs of pilots on board (one working, one resting), but cabin crew members cannot be expected to do an 18 hour shift.
So crews would be "slipped" as described above on the westbound but also on the eastbound, meaning a crew change in DUB in both directions.
It would be similar to LHR-SIN-SYD/SYD-SIN-LHR on BA or AKL-LAX-LHR/LHR-LAX-AKL on NZ, or the former AI BOM-LHR-JFK/JFK-LHR-BOM.
If the service is not daily, as in the above mentioned examples, then the cres are going to enjoy longer layovers, 2 in DUB and 1 in LAX and be away from home for over a week.
Pleasant cities for layovers, could be lucrative in allowances, reckon many crews will like this gig.