I’ve largely kept my peace on this topic because my personal opinion is somewhere in the range of what the OP describes. Intellectually, I know this is something the Night Elf fans probably deserve, and so I shouldn’t begrudge them that. On a gut level, I hate it. But it wasn’t until I thought about it a little bit that I realized why this (and something else, which I’ll get to below) bother me so much.
The Terror of Darkshore and Umbric’s raising of the Void Rex are two things that are just dark enough to have an interesting flavor to them, but aren’t so dark that it overwhelms the presentation of the event. In both cases you have an Alliance figure doing something that would ordinarily be pretty nasty, but the presentation of them is such that Alliance players can feel good about corrupting a loa’s children or burying their enemies alive.
Think about if the roles were completely switched - if the Horde corrupted the eggs of a Wild God and entombed some random soldier to die in a gruesome way. What do you think you would see that was different from the Alliance version? My guess is this - you would see the event presented in such a way that makes you sympathize with the horror the victim is suffering. That as an Alliance player you’d feel angry and as a Horde player you’d feel guilty. This same dynamic played out in the War of Thorns - killing the NE mobs laid on the pathos so thick it was jarring.
In a nutshell, the Alliance now gets to do cool, darker things without having to feel bad about themselves. The Horde can seemingly do nothing without the writers dragging the player through doubt and guilt.