From the schedule it seems that the A321 operates the 710 and 725 pretty consistently over the winter on weekdays. Other flights are more random and appear to vary week by week. I don't know if the A321 goes to the canaries on weekends?
As you say the A321 is pretty maxed out from DUB over the summer, especially now that they have only the three of them.
Any news of the ATR-600s are going to be seen at ORK anyone soon?