Actually, the red-capped mangabey was the last new mammal species to arrive in Dublin, coming in 2014, a year after the okapi. You might have forgotten them as a) they live with the gorillas and b) they are closely related to the white-crowned mangabeys that were already living at the zoo. And this is just with regards to mammals. The citron-crested cockatoos arrived in 2016, and I think some of the reptiles in Zoorassic World weren't already living in the old reptile house before the former opened in 2017 (correct me if I'm wrong).
Anyway, I was surprised that the dholes have just arrived, since I first heard about the zoo's plans to get them when I visited around christmas - less than two months ago! I'm undoubtedly very excited and hope to visit the zoo again sometime soon to see them, as dholes are a species I have yet to see.
The five dholes are all male and came from Tierpark Berlin a few days ago, and consist of two 6-year old brothers, two 3-year old brothers and one 5-year old half-brother.
Dhole Delight! - Dublin Zoo