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I've realized that this may come across as more aggressive that I originally intended. If so, then I apologize.
Er...yes, yes it did. Apology accepted though!
I don't doubt that Dorian's got a serious self-destructive streak - he even tries to nuke a relationship he really wants, after all, out of a twisted sense of "I'll rip out my own heart rather than wait for you to do it for me". And he's a product of Tevinter society - I don't think he's been living like a monk all of these years. If he's really written off long-term emotional attachments as Something People Like Me Don't Have, going to brothels would be a pragmatic thing to do.
But I've read the WoT Volume 1, and there are entries in that which are deliberately written to showcase the speaker/writer's bias (Blackwall's "screw Ferelden, they did it to themselves" address comes to mind). It's a stylistic choice - the conceit of the book is that it's a collection of documents from Thedas, and each individual writer has their own biases...and so does the person analysing the "found document". It's why two historians can use the same document to "prove" two diametrically opposed points.
For example...define "debauchery." If the Dorian's entry is 100% accurate, and he was getting hammered in elven brothels every single night, then I think most of us would agree that the term "debauchery" is warranted...especially given the status of elves. Dorian himself is fairly disgusted by his own behaviour post-Alexius craziness, so we know he screwed up. However, if someone is viciously homophobic, any gay relationship could get lumped into that category. If you really don't like someone, you could probably find an excuse to file fairly mild or occasional behaviour into "debauchery." My question, then, was whether the author of Dorian's entry had their own agenda, or if it was intended as purely neutral. After rereading, I'm more inclined to believe that the (real-life) writers had a persona in mind.
Alexius' letter is probably mostly true, at the very least. However, the writer of Dorian's entry in the book (who never identifies themselves, if I recall..?) puts his own interpretation of things on top of that. He also doesn't appear to know about the blood magic ritual...whereas the ACTUAL writers of the game most definitely do. It's related to what the TV Tropes wiki would call a Watsonian vs Doylist explanation - is the text an "in-universe" one, or strictly the word of the creator? I tend to group WoT as the "Watsonian" explanation and devs' blogs+the art books as "Doylist". Hence my comment that the extract was a bit like a "gossip column" entry; if it's from Tevinter, and allegedly written by someone who supports the system that Dorian is working against, they will probably have a particular spin on the events that they learn about. They may repeat rumours or outright lie. On the flip side, I personally think that Dorian uses alcohol as a crutch, but is not yet a full-blown alcoholic. He certainly is in danger of becoming one, but he's not quite there yet. Gaider appeared surprised when someone asked him if Dorian was alcoholic, so I take that as a "Doylist" source. There is, however, plenty to work with for those who think he is an alcoholic.
In WoT, we get "You asked about that young nutter who ran off to the South to cause trouble. Well, here's the word on the street." It's different from David Gaider or Patrick Weekes writing a straightforward entry that says "Here is Dorian. In his youth he (insert past here). He is written as (alcoholic/racist/self-destructive/a slavery apologist/whatever) because we wanted to explore (themes) in this game". It's also different from the art book, which was very much behind the scenes, here-is-where-we-were-going-with-this-character. In short, it's a creative writing exercise, not a documentary.
And on an unrelated note, I love the idea of young Dorian causing merry hell in the Circles. Because of course he would.