Ok, so first off being Gen 8 mechanics or Gen 4 mechanics doesn't matter, because the Quick Ball has not changed at all since it's release.
If you haven't got a switch yet its your fault it's been out for four years...
Every roaming legendary has the same catch rate, (Raikou, Entei, Suicune, Articuno, Zapdos, Moltres, Mesprit, Cresselia, Latias, Latios have a catch rate of 3.)