I think for me its the fact that currently Xal’atath’s entire shtick is just Jailer (Female Elf) at the moment. Step-for-step she is, functionally, the exact same character as Zovaal, just tied to the Void instead of Death.
Ancient Evil 
Locked Away for the Safety of the Universe
Has A Plan For Azeroth to Destroy the Universe
Talks Ominously About Unseen Threats That Justify Their Evil
Monologues About How Long Their Plan Has Been Planned
Monologues About How Much Better They Are Than All Those Other Villains
Monologues About How They Are Misunderstood And We’re The Bad Guys Actually
Convoluted Manipulation Plot That They Will Insist Was Masterfully Planned
Has A WoW Elf Ranger Chasing Them Down And Also Maybe Serving Them
The WoW Elf Ranger Takes Increasingly Extreme Actions For/To Stop Them
Was Somehow Here All Along Planning For Millenia
Somehow Never Did Anything During Their Millenia of Planning