Edit: resolved. I assumed the main questline was complete when I received the last tablet for the Hall of the Lunar Champion.
I've been to the Senchel palace terrace multiple times, both immediately after I completed the main questline and after relogging. (I've completed the main questline in northern Elsweyr as well.) There is no "hero" NPC showing up for me. I've searched for a solution but all I've read is that a cat shows up and leads you to a khajit.
Sky above, Earth below, Fire within PSN: MirthfaeryEl-Rielle the Awakened, High Elf Sorceror
Quiet Panda, Khajiit Sorceror
Twizzy Stardusk, Bosmer Sorceror
S'ilence, Khajiit Nightblade
Indiguana Jones, Argonian Nightblade
Angelienne, Breton Templar
Holy Meow, Khajiit Templar
Mookie Farkle, Argonian Dragonknight
S'pawk, Khajiit Dragonknight
Atha'zagora, Khajiit Arcanist
Mokey Fraggle, Argonian Warden
Bumfuzzle Briar, Khajiit Warden
Nandailie Resinator, Dark Elf Necromancer
Faerylicious, Orc Necromancer