No. My understanding is as follows.
Border control will still apply at the airport of arrival DUB. Irish authorities would need to be satified that passport and VISA were valid even if this was a flight transfer. DUB - LHR is non domestic intra european. In Shengen Countries EU pax can travel freely across boundaries without Passport control but UK is Non Shengen. Therefore all arriving pax ofrom outwith UK are effectivley subject to passport control. This would include anyone travelling ona non EU passport.
All pax entering EU and UK are notified by airlines to border control. i.e. Immigration know who is coming before you get to the passport desk. Unless there is a physical need to check documents I assume they will only filter check papers - random.
At LGW were domestic pax mix with international pax e.g. at S terminal arriving Squeezy jet pax mix with departing pax in a common departures/arrival area. There was a potential risk that pax from say Barcelona could swap boarding cards with pax to Glasgow, before Passport control. This would ppotentially allow an illegal to board ona false passport at Barcelona and then avoid passport control on a domestic link LGW tpo GLA.
The photo ID/ Landing card check provides a means to ensure that all arrivals do in fact pass from the aircraft to landside. Any swap of Info would show up at the check where the operator can reconcile the bar code with a photo. Missing pax or wrong ID's will show up.
At other UK airports where pax mix there is less chance of this happening as , from a common lounge, individual gates are policed by airline staff. Boarding card/ photo ID and passports are checked depending on final destination of the flight. Remember, carrying someone without appropriate documentation will land the Airline with cost of repatriation etc.