What if all the "Death Realm" shenanigans are the "dead" Old Gods' spirits causing a bunch of crazy evil nonsense from the other side of the realm of existence, much like they did when they were imprisoned on this side of existence.
Yoggy does have that habit of entering realms he shouldn't & mucking them up quite a bit. Man Ulduar was such a fun trailer and patch has to be among my favorites in Wrath of the Lich King. The trailer was especially my favorite with Thrall, Jaina, Varian, Garrosh and the rest!