Hi!
In your ending Lucian becomes depowered and turns into a mortal. But it's kept a secret so that he can continue to rule. Malady's story is never resolved no matter what you do, so don't bother looking for answers. Although in your case she is screwed for good since you are powerless and can't help her in her quest.
Gareth got purged because you didn't convince him to abandon revenge against the Order. The only way to save him is to persuade him to stand down when you meet him and Alexandar on Nameless Isle. If you don't then he continues to fight them, gets captured off-screen and turned into a Silent monk.
Don't know what's up with the endings
![smile smile](/images/graemlins/default_dark/smile.gif)