You’re still doing double standards; Syiax admitted he’s doing what you criticize me for, but you don’t call him out.
Illidan and Sylvanas have quite a bit in common. I went over their traits in a thread.
The thing that makes it feel more like a victory for Illidan is that he gets exactly what he wanted. He gets to stay and guard Sargeras and which him suffer in his imprisonment. That’s a huge win for Illidan.
And World of Warcraft’s morals have often been built on double standards (maybe that’s why certain people on the forums keep using double standards in their arguments - like calls to like). I made a thread on that problem with the story too.
Killing Xe’ra is also absurd from a story perspective because she’s the most powerful representative of the Light encountered thus far. And not only is she jobbed, but it’s also a one-hit-kill. Illidan is not invincible - in the Harbingers’ cinematic a Pit Lord manages to knock him on his butt despite Illidan being a demon-killing specialist and a Pit Lord being a demon. In fact, those same eyebeams that job Xe’ra only scratch the Pit Lord. All this can be seen here;
If the writers want to villain bat Xe’ra, they’ve destroyed the idea that she can be a threat. Of course, that’s still a major double standard that some want to sweep everything Illidan did under the rug while at the same time cheering for the gratuitous demise of someone who was, at worst and to throw certain people a bone, a lesser evil.