Is Nightslayer the only PvP realm? (besides Maladath AU)
Pretty much. Blizz might add a RP-PvP realm in the future, but that’s about it. 
Ok. A handful of realms appeared when I loaded into Nightslayer and thought there were full/closed realms from Thursday lol
Yeah my client did a weird thing where it merged anniversary and hardcore as I saw the realms all mashed together before it reloaded.