I'm not comparing their complexity. I am comparing how much of an asspull they are. Void Elves were pulled out of thin air to please High Elf fans, and for equality since Horde got Nightborne. While the Jailer was also pulled out of thin air, for Sylvanas. I argue the Jailer fits into the overall story much better than random elves studying the void at the same time Alleria was, and coincidentally meeting up.
Also, Umbric has hardly any character other than "Alleria's Sidekick" who helped the Alliance resurrect some dinos and kill some goblins. How is that any more impressive than the Jailer? Who is Sylvanas' boss who helped her with his Mawsworn army and steal some sigils.