While trying to free up VRAM I disabled all mods and went from Ultra settings to High....the buildings started disappearing again.
It is completely dependant on camera angle and it isn't distance as the guard climbing the stairs disappears too and he isn't that far from me.
Has anyone else had these buildings disappear from the top of Dragonreach stairs? I cannot isolate this and it only seems to happen when I am running at lower graphics settings, not higher settings as would be logical.