Don't know for sure.
AA.com says:
When you check your luggage, the airport agent will put a bag tag on each bag that indicates your name, the flight number(s), and all cities in your ticketed itinerary. This information comes from our Sabre® computer reservation system.
Tip: If you are deviating from your ticketed itinerary, please advise the airport agent before checking your luggage.
I once flew DFW-LAX-AKL-BNE-SYD-MEL and my bags were checked all the way through. The AKL stop didn't involve a change of planes, so it's likely that my bags were tagged as DFW-LAX-BNE-SYD-MEL.
I wonder if you could take advantage of the tip above and request that your bags be sent from LHR-DUB and not make the LHR-AMS-LHR-DUB part of the journey. Probably not since it's an international trip, but it might be worth asking.
-z