EI-RB
You are correct that the utilisation of the BFS EI A320 is poor. However, for the most part their hands are tied on this. The LHR schedule is not very flexible re landing and take off times.
In addition, because no other short routes are available the max daily rotations that EI can get in including a sector like BFS ACE is 2.
I dont see that this will increase. The closest routes that are slightly shorter are CDG and AMS both of which are either being discontinued or gone already.
In Dublin it is not so slack in terms of utilisation.
EI-BUD