The original Karazhan raid was released during World of Warcraft's first expansion pack, Burning Crusade, in 2007. One of the haunted tower's many wings was ostensibly a brothel, populated by dozens of ghostly female concubines clad in suggestive clothing. As of this PTR build, about half of those ghosts have been replaced by male counterparts, and nearly all of them have had their names altered in some way.
The area previously had three different types of enemies that would appear, some of which would transform into monsters after taking enough damage, and all of which have been changed in some way. The Wanton Hostess has been renamed Wanton Host, which uses a male model and transforms into a gender neutral wraith instead of a banshee. The Night Mistress enemy is still present, but a male counterpart, called the Night Lord, has joined them. Lastly, the Concubine enemy has seemingly been split into two separate enemies: the female Zealous Paramour, who turn into a succubus when wounded as their predecessor did, and the male Zealous Consort, who become satyrs.
Karazhan is not the only raid to undergo such changes. The Black Temple raid, which appeared in the same expansion pack, had a similar area called the Den of Mortal Delights, filled with enemies called Temple Concubines. These mobs have also had men added to the previously female cast, and have been renamed Temple Acolytes.
Recently, Blizzard has made a number of similar changes, from removing emotes that could be used to harass other players to censoring names, designs, and even in-game paintings. While some of these changes have been met with confusion, anger, or derision, this change is being received with near universal positivity. Longtime fans of World of Warcraft are not asking for censorship–they're asking for equality. Equal-opportunity changes like this one give off an impression that hopeful, positive change might still be possible.
Still, this change is leaving many scratching their heads. One has to wonder how many people the changes to 14-year-old raids will truly affect. While thousands of players battled through these halls in the past, the ancient content is far from relevant now, and the majority of players will likely never see these new enemies. Nonetheless, these changes were simple, and undoubtedly took little effort for the World of Warcraft developers. It is unlikely this is the last of such alterations, and it remains to be seen if Blizzard makes a statement of the intentions behind all of this. Until then, all anyone can do is speculate.