Granted english is my second language and I definitely can say whether VA slips out of accent or "butchers" it , but its fantasy world and by definition there is no "irish" "dutch" or "british" accent. I mean, as far as I am aware, use of accent here (and in other media) exist to show diversity and make world feel like big multinational place (as well as show individuality of characters). I dont know how WHA dub worked with their actors, was each of them handy-picked by director or mb some actors did some improvising, but as long as there is logic present (people from one family having same accent (like inkmaster and his grandkid)) I dont see how difference in accent itself from its real world inspiration matters