"Easily my favourite of the ones I used was Dorian, the amusingly moustached Tevinter mage and the Inquisition's designated snarker (also BioWare's first gay party member, though that only really comes up in his personal quest - a somewhat on-the-nose PSA with experience points)" - Eurogamer
"The writing at times can slip depending on the character (Varric and Dorian are always great) (...)" - Destructoid
"It’s a shame too, because all the main characters are well-written and acted - particularly Dorian, whose familial struggles provided some genuinely emotional moments." - IGN
"Hearing Sera try to get Cassandra to guess her birthplace, or the attempts to get Dorian to realize how pompous he is can be hysterical and ensures, even during the hours of serious demon slaying, the chemistry between characters is lighthearted." - Hardcore Gamer
"(...) en is mage Dorian een necromancer, waardoor hij zelfs als hij dood is nog door kan vechten." - XGN (translation: "and mage Dorian is a necromancer, which means he can continue fighting even when he's dead" (curious how that's going to work))
I think the general consensus is that Dorian is a very well-written character 