RyanAir arrives in T1, Delta departs out of T2. You're talking waiting for bags, terminal change, check in for new flight and drop bags, along with customs and immigration since DUB is a preclearance location. Tell them to enjoy spending the rest of the day/night in the airport! The 11:45am DUB-JFK flight is the last Delta flight out for the day.

According to the Delta website, minimum check-in time is 75 minutes before departure-even if not checking bags. That gives them 30 minutes from scheduled arrival to needing to be checked in at the Delta counter.

Why do people keep booking short connections to 1x daily international flights on different carriers, especially when coming from a LCC that won't care about your next flight?