And there is the difference in expectations where it comes to writing. I think that Arueshalae is a badly written fanservice character, and one of the reasons why WotR's writing is mediocre. She constantly tells the main character how she struggles against her demonic nature, yet those struggles are not reflected in the reality; your character is never in danger of her. Neither is she really: whenever she is about to die in battle, Desna intervenes to magically teleport her away. She is a demon, yet faces no persecution in your city that was just liberated from demons; the inquisition that persecutes even tieflings because of their heritage, is strangely absent here. She constantly talks about earning redemption herself, yet is codependent on the main character to the point where frankly I've thought it unhealthy. If this were a fanfiction, I'd say Arueshalae is a Mary Sue.
Hmm. Guess I'll go into spoiler territory a bit.
There's a bit of major reactivity with her (and a few other party members). Depending on what you tell her throughout the game, there's actually a way to have her reverse course and slide back into full demon. She will leave your party during chapter 4 for a brief while if this happens. However, depending on your mythic path, she may leave your party permanently if this happens. If you are on the demon mythic path and commit to full demon during chapter 5 and you have her on the redemption path, she will also permanently leave your party then.
Desna's protection only applies for chapters 2 and 3 because she's a plot important character during that phase of the story. She loses that protection from chapter 4 onwards, and tells you as much if you talk to her then.
Also, when people praise WotR's writing, it's more from the standpoint of the party interactions, which are undeniably among the most lively and frequent in the entire gaming industry. The actual quality is subjective. The sheer frequency and variety does lots to elevate the companions into something greater, and is also an indirect way to add additional depth to them all.