I think there's little doubt that a daily service stimulates extra demand than 3 or 4 flights weekly on long haul. Importantly, this probably applies more to business travellers paying premium fares as it gives greater flexibility when booking a trip; but also if their meetings overrun or finish early, they know they can try and catch a flight the next day or the previous day (if not full!). A daily can also provide better options for onward transfers at Hong Kong if those connecting flights are not daily.
It's not so bad as it is as they can just bung pax on a BA shuttle and stick them on one of their own flights from LHR (5 x daily brings some flexibility).
So you would go to so much trouble just to avoid Manchester which is just down the road?
You would fly LPL-DUB-LHR-XXX ?
Sounds like a case of saving cash more than anything - everybody knows the difference in price is huge when starting ex DUB (indeed I've done it a couple of times myself and picked up J for the price of a Y ticket out of MAN).