Originally Posted by
1Aturnleft
DUB-LHR-DUB can be had from around €80rtn on BA earning 5 tier points in each direction....
The OP said they were positioning to DUB for this trip so presumably they would be more likely to do a LHR-DUB-LHR (or whatever UK base they start from).
Those are likely to be a bit more pricey, but a short trip like that is looking like the only way if the airport upgrade isn't forthcoming.