EI flies A332s from DUB to LAX (I've even seen t/a departures from Rwy 16) and DL has flown 777s from DUB to ATL, n/s, so the runway length at DUB would not be a factor working against DUB; DXB really isn't such a long route.
It was disappointing that EK failed to add DUB again, but there are other airlines. There is now a recognition in govt circles that Ireland needs a direct route to Asia and hopefully, this can give rise to a package of incentives which can be offered to carriers such as SQ, TG, MH, CX etc - possibly EK as well. If the DUB airport authority could work with bodies involved in trade and tourism, I'm sure a package of suitable incentives could be put together.