Missing 1 black tusk and 2 hyenas but have recently killed random bosses for those factions and no cards dropped. I completed the sets on XB in the level 30 days so it wasn't something I was really looking to do on PC; I just got them as i got them. Now I'd just like to complete the missing factions but don't necessarily want to set a 30 min timer if they're bugged.
Also make sure your killing it in the relevant zone. The Playing Cards (Hearts, etc) are DC bosses ONLY and the Arcana Cards (Hermit, etc) are NY bosses ONLY. (world bosses are on a 30min CD). Location in area doesn't matter as any can spawn at any of the spawn spots and spawn based on the HOSTS missing cards.