Note that AA have more than one sort of long haul J seat.
I plugged in some random dates - DUB-MCO-DUB comes back at EUR1332 whilst DUB-MCO-NCL (via JFK and LHR) is EUR1555.
For the avoidance of hassle, you may prefer to book an open jaw like that. You would save 9,000 Avios plus £25 from a one way J redemption DUB-LHR-NCL (so value that at £125). Means you only pay about an extra £65 for the convenience of not having to go through Dublin on the way home AND you get a through ticket.
Another option is to book AA into Dublin, then onward via LHR to London (but now you're up to 4 flights) AA will look after you if you misconnect even on two separate tickets, but Dublin is an outstation and you might struggle to convince someone of the rules!