A temple of death & undeath would require a morgue/raising room, for the studies of anatomy, building and/or generating their undead servants.
I would recommend a separate/different room - for the "death" side, for the burial preparations. Do they do embalming? Cleaning & dressing for burial? Fluid draining? Does the area/culture/religion engage in mummification?... Anyway, some room or set of rooms(an entire floor?) for autopsies, storage, and examinations of dead bodies....perhaps before they are sent over to the "raising room" to be turned into undead.
If there are "fiends" running around/in the service of this order [whether or not that is willing], then before a "scrying room" I would make sure there is a "conjuring/binding chamber"...which could double as your scrying room...maybe instead of a "pool of blood" or entrails altar or whatever, you summon a demon/devil/other to tell and/or show you what you want to know.
Living quarters are likely to be minimal: "cells" (probably not more than a broom closet) for the rank and file. Decent individual rooms for the 5 seniors. Full suite, probably on his own floor, multiple chambers, for the high priest.
Also, magic world or no magic world...any communal living sitch' needs adequate bathing and, um, "facilities" facilities.